Method and apparatus for exchanging variable length frames by fixed length cell handling exchange

ABSTRACT

The invention provides a variable length frame exchanging method adapted to a fixed length cell handling exchange into which a terminal for use with a data communication method by a variable length frame is accommodated, a variable length frame exchanging interface apparatus and a call acceptance determination system, which are improved in that a variable length frame can be exchanged at a high speed in a fixed length cell handling exchange network and a terminal can be connected to and accommodated into the exchange in the same conditions as an existing service. The terminal is connected to the exchange by way of a subscriber line including a plurality of channels. A variable length frame from the terminal is disassembled into fixed length cells, and a use channel number or numbers and a DLCI of the subscriber line are converted into a VPI and a VCI. The VPI and the VCI are added to each of the fixed length cells, respectively, and the resulted fixed length cells are inputted to the exchange so that the frame is exchanged by the exchange.

BACKGROUND OF THE INVENTION

This invention relates to a variable length frame exchanging method, avariable length frame exchanging interface apparatus and a callacceptance determination system adapted for a fixed length cell handingexchange in which a terminal for use with a data communication system bya variable length frame is accommodated.

In recent years, as the introduction of the ISDN (Integrated ServicesDigital Network) proceeds, the utilization of public networks iscomplicated such that a public network, which has offered only telephoneservices, can now offer such various communication services as datacommunications, facsimile communications and packet communications athome of each of subscribers. Further, as the amount of communicationsincreases, not only speech but also video signals and so forth can betransmitted. In this manner, various information communications areavailable nowadays. Particularly it is advantageous in terms of the costand/or the communication speed to communicate data by way of an ISDN.

Meanwhile, the CCITT recommends a data communication method by avariable length frame including logic channel information, for example,a frame relay, for data communications. The frame relay is adapted to acommon packet exchanging system and is expected as a technique whichmeets the requirement for a high speed packet service. In the framerelay technique, no protocol for a layer higher than the layer 2 isdefined and the network does not participate in the protocol since framemultiplexing is performed in the data link layer, and accordingly,hardware matching is easy comparing with a packet exchanging systembased on the X25 which is a protocol for the layer 2 and an increase inthroughput can be realized.

Further, in popular packet exchanging systems, repeat control based on aprotocol of a LAP-B is performed between a terminal and a network(exchange) or between different exchanges. With a frame relay, however,repeat control is not performed between a terminal and a network, andconsequently, high speed transmission can be achieved together with anadditional reason that no controlling processing for the repeat controlis required.

By the way, in recent years, an ATM (Asynchronous Transfer Mode)exchange technique has been consented as a next generation exchangesystem by the CCITT, and investigations have been and are being directedactively toward the ATM exchange technique as a technique which realizesa broad band ISDN (B-ISDN). With an ATM exchange (fixed length cellhandling exchange), user information is exchanged in the form of apacket of a fixed length called cell which includes united contents(data, sound, images and so forth) of information. As development ofsuch ATM exchange technique proceeds, it is desired that also theservice for accommodating and connecting a terminal (hereinafterreferred to as frame relay terminal) for a frame relay described aboveinto and to an ATM exchange network can be offered as one of services ofthe ATM exchange network.

An example for reference of a system wherein an ISDN frame relay is usedto interconnect a plurality of LANs (Local Area Networks) is illustratedin FIG. 44. Referring to FIG. 44, a plurality of personal computers(frame relay terminals) 11 to 16 are shown, and a LAN 21 is constitutedfrom the personal computers 11 and 12; another LAN 22 is constitutedfrom the personal computers 13 and 14; and a further LAN 23 isconstituted from the personal computers 15 and 16. The LANs 21 to 23 areconnected to exchange offices 51 to 53 by way of ISDN interfaces 31 to33 and circuit terminating equipments (NT) 41 to 43, respectively, sothat they are connected to each other by way of a public network (ISDN)60.

In such a system as described above, establishment of a transmissionchannel is performed using a call control protocol (I.451), but atransmission channel may otherwise be established in response to acommand from a service person. Meanwhile, a LAP-F (Link AccessProtocol-Frame Relay) is used for frame transmission (popular packettransmission). Data transmission is thus allowed between arbitraryterminals (personal computers 11 to 16). In particular, each of thepersonal computers 11 to 16 can communicate with an arbitrary one of theother personal computers 11 to 16 by performing data communication byway of a logical link (identified with a DLCI (Data Link ConnectionIdentifier) in the signal) number of the LAP-F applied on thecommunication channel.

In this instance, the transmission channel between any one of the LANs21 to 23 and a corresponding one of the exchange offices 51 to 53 canhave an arbitrary line speed, and each of the LANs 21 to 23 can select adesired line speed. For example, a PCM circuit (24 channels or 30channels) is used for the interface with each subscriber, and arbitrarychannels desired by the subscribers can be combined to determine a linespeed. In short, a subscriber can select a line speed from among up to64×24 channels (or 64×30 channels) to the utmost.

However, where the network shown in FIG. 44 is a broad band ISDN whichmakes use of an ATM exchange, a frame relay has a subject to be solvedin that, since it involves a variable frame length similarly to that ofthe popular packet exchange system X25, it cannot achieve high speedexchanging processing comparing with switching which employs a packet(cells) of a fixed length such as in an ATM.

Further, the CCITT does not involve provisions for the inside of anetwork (that is, for the inside of an exchange) when a frame relayterminal is accommodated into an ATM exchange, and the method ofrealizing such accommodation depends upon the maker of the system. Forexample, in the system shown in FIG. 44, a communication channel isconnected between arbitrary ones of the subscribers (personal computers11 to 16), and when any of the subscribers tries to transmit data to theother party, a function of routing to the other party designated by aDLCI number is required.

Meanwhile, in order to accommodate a frame relay terminal into an ATMexchange and set a path, a system has been proposed wherein acceptanceof a call is determined from a peak value (a value reported from theuser) of a band used between terminals between which communications areto be performed and a band for the path is allocated in accordance withthe determination. Accordingly, when a user of a frame relay terminalmakes a request to set a path of a band higher than a physical linespeed (physical maximum speed), the path cannot be set nor connected.

However, a frame relay service allows, in most cases, the contract ofgenerally 200 to 300% of the physical line speed, and also when a framerelay service is offered with an ATM exchange, the conditions must bethe same as those in the existing service. Therefore, when a frame relayterminal is to be accommodated into an ATM exchange, it is desired toallow determination of acceptance of a call from a frame relay terminalwhile adopting the same conditions as those of the existing frame relayservice.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a variable lengthframe exchanging method and a variable length frame exchanging interfaceapparatus by which a frame having a variable data length can beexchanged at a high speed in a fixed length cell handling exchangenetwork.

It is another object of the present invention to provide a callacceptance determination system wherein a path for a variable lengthframe can be set in a fixed length cell handling exchange network in thesame conditions as those in an existing service to realize a service forconnecting and accommodating a variable length frame terminal to andinto the fixed length cell handling exchange.

In order to attain the objects described above, according to an aspectof the present invention, there is provided a variable length frameexchanging method by a fixed length cell handling exchange which handlesfixed length cells each including a logic channel information sectionand a data section and to which a terminal for use with a datacommunication method by a variable length frame including logic channelinformation is connected by way of a subscriber line having at least onechannel, comprising the steps of disassembling, when a transmissionframe is transmitted from the terminal to the exchange, the transmissionframe into fixed length cells, converting a channel number or numbers ofthe subscriber line which has been used to transmit the transmissionframe from the terminal and data link connection identifier informationas the logic channel information added to the transmission frame intocommunication channel identifier information for the logic channelinformation sections of the fixed length cells, adding the communicationchannel identifier information to the logic channel information sectionof each of the fixed length cells and inputting the fixed length cellsto the exchange, and exchanging the frame from the terminal as the fixedlength cells in accordance with the communication channel identifierinformation by means of the exchange.

The communication channel identifier information may include virtualpath identifier information and virtual channel identifier information,and the channel number or numbers of the subscriber line which have beenused to transmit the transmission frame from the terminal may beconverted into virtual path identifier information while the data linkconnection identifier information to be added to the transmission frameis converted into virtual channel identifier information.

According to another aspect of the present invention, there is provideda variable length frame exchanging method by a fixed length cellhandling exchange which handles fixed length cells each including alogic channel information section and a data section and to which aterminal for use with a data communication method by a variable lengthframe including logic channel information is connected by way of asubscriber line having at least one channel, comprising the steps ofproducing, when fixed length cells designating the terminal as adestination of transmission are outputted from the exchange to thesubscriber line, a call-in frame from the fixed length cells, convertingcommunication channel identifier information of the logic channelinformation section of each of the fixed length cells into data linkconnection identifier information and a channel number or numbers of thesubscriber line which are available to transmit the call-in frame to theterminal, and adding the data link connection identifier information aslogic channel information to the call-in frame and transmitting thecall-in frame to the terminal using a channel or channels of the channelnumber or numbers of the subscriber line obtained by conversion from thecommunication channel identifier information.

The communication channel identifier information may include virtualchannel identifier information and virtual path identifier information,and the virtual channel identifier information may be converted intodata link connection identifier information while the virtual pathidentifier information is converted into a channel number or numbers ofthe subscriber line which are available to transmit the virtual pathidentifier information to the terminal.

According to a further aspect of the present invention, there isprovided a variable length frame exchanging method by a fixed lengthcell handling exchange which handles fixed length cells each including alogic channel information section and a data section and to which aterminal for use with a data communication method by a variable lengthframe including logic channel information is connected by way of asubscriber line having at least one channel, comprising the steps ofdisassembling, when a transmission frame is transmitted from theterminal to the exchange, the transmission frame into fixed lengthcells, converting a channel number or numbers of the subscriber linewhich has been used to transmit the transmission frame from the terminaland data link connection identifier information as the logic channelinformation added to the transmission frame into communication channelidentifier information for the logic channel information sections of thefixed length cells, adding the communication channel identifierinformation to the logic channel information section of each of thefixed length cells and inputting the fixed length cells to the exchange,and exchanging the frame from the terminal as the fixed length cells inaccordance with the communication channel identifier information bymeans of the exchange, but producing, when fixed length cellsdesignating the terminal as a destination of transmission are outputtedfrom the exchange to the subscriber line, a call-in frame from the fixedlength cells, converting communication channel identifier information tobe added to the logic channel information section of each of the fixedlength cells into data link connection identifier information and achannel number or numbers of the subscriber line which are available totransmit the call-in frame to the terminal, and adding the data linkconnection identifier information as logic channel information to thecall-in frame and transmitting the call-in frame to the terminal using achannel or channels of the channel number or numbers of the subscriberline obtained by conversion from the communication channel identifierinformation.

The variable length frame exchanging method may be constructed such thatthe communication channel identifier information includes virtual pathidentifier information and virtual channel identifier information, and afirst corresponding relationship between the virtual path identifierinformation and a channel number or numbers of the subscriber line usedbetween the terminal and the exchange and a second correspondingrelationship between the virtual channel identifier information and adata link connection identifier to be added to a frame are registered inadvance, and wherein, when a transmission frame is to be transmittedfrom the terminal to the exchange, a channel number or numbers of thesubscriber line which have been used to transmit the transmission framefrom the terminal is converted into virtual path identifier informationin accordance with the first corresponding relationship and data linkconnection identifier information to be added to the transmission frameis converted into virtual channel identifier information in accordancewith the second corresponding relationship, but when fixed length cellsdesignating the terminal as a destination of transmission is outputtedfrom the exchange to the subscriber line, virtual channel identifierinformation to be added to each of the fixed length cells is convertedinto data link connection identifier information in accordance with thesecond corresponding relationship and virtual path identifierinformation to be added to each of the fixed length cells is convertedinto a channel number or numbers of the subscriber line which areavailable upon transmission to the terminal in accordance with the firstcorresponding relationship.

According to a still further aspect of the present invention, there isprovided a variable length frame exchanging interface apparatus which isinterposed in a subscriber line having at least one channel forinterconnecting an exchange which handles fixed length cells eachincluding a logic channel information section and a data section and aterminal for use with a data communication method by a variable lengthframe including logic channel information and performs conversionprocessing between fixed length cells for the exchange and a variablelength frame for the terminal, comprising frame production means forproducing a transmission frame based on data transmitted thereto fromthe terminal by way of a plurality of channels of the subscriber line,channel number to virtual path identifier information conversion meansfor converting a channel number or numbers of the subscriber line whichhave been used to transmit the transmission frame from the terminal intovirtual path identifier information as communication channel identifierinformation for the logic channel information sections of fixed lengthcells, data link connection identifier information to virtual channelidentifier information conversion means for converting data linkconnection identifier information as logic channel information to beadded to the transmission frame into virtual channel identifierinformation as the communication channel identifier information for thelogic channel information sections of fixed length cells, andtransmission frame disassembling means for disassembling thetransmission frame into fixed length cells to which the virtual pathidentifier information obtained by conversion by the channel number tovirtual path identifier information conversion means and the virtualchannel identifier information obtained by conversion by the data linkconnection identifier information to virtual channel identifierinformation conversion means are added and sending out the fixed lengthcells to the exchange.

The channel number to virtual path identifier information conversionmeans may include first storage means for storing in advance a firstcorresponding relationship between a channel number or numbers of thesubscriber line which are used between the terminal and the exchange andvirtual path identifier information as communication channel identifierinformation, and the data link connection identifier information tovirtual channel identifier information conversion means may includesecond storage means for storing in advance a second correspondingrelationship between a data link connection identifier to be added to aframe and virtual channel identifier information as the communicationchannel identifier information.

According to a yet further aspect of the present invention, there isprovided a variable length frame exchanging interface apparatus which isinterposed in a subscriber line having at least one channel forinterconnecting an exchange which handles fixed length cells eachincluding a logic channel information section and a data section and aterminal for use with a data communication method by a variable lengthframe including logic channel information and performs conversionprocessing between fixed length cells for the exchange and a variablelength frame for the terminal, comprising frame assembling means forassembling a call-in frame based on fixed length cells from the exchangedesignating the terminal as a destination of transmission, virtualchannel identifier information to data link connection identifierinformation conversion means for converting virtual channel identifierinformation as communication channel identifier information for thelogic channel information sections of the fixed length cells into datalink connection identifier information as logic channel information tobe added to the call-in frame, virtual path identifier information tochannel number conversion means for converting virtual path identifierinformation as the communication channel identifier information for thelogic channel information sections of the fixed length cells into achannel number or numbers of the subscriber line which are availableupon transmission to the terminal, and call-in frame disassembling meansfor transmitting the call-in frame, to which the data link connectionidentifier information obtained by conversion by the virtual channelidentifier information to data link connection identifier informationconversion means is added, by way of a channel or channels correspondingto the channel number or numbers of the subscriber line obtained byconversion by the virtual path identifier information to channel numberconversion means to the terminal.

Preferably, the virtual path identifier information to channel numberconversion means includes first storage means for storing in advance afirst corresponding relationship between virtual path identifierinformation as the communication channel identifier information and achannel number or numbers of the subscriber line which are used betweenthe terminal and the exchange and the virtual channel identifierinformation to data link connection identifier information conversionmeans includes second storage means for storing in advance a secondcorresponding relationship between virtual channel identifierinformation as the communication channel identifier information and adata link connection identifier to be added to a frame.

According to a yet further aspect of the present invention, there isprovided a variable length frame exchanging interface apparatus which isinterposed in a subscriber line having at least one channel forinterconnecting an exchange which handles fixed length cells eachincluding a logic channel information section and a data section and aterminal for use with a data communication method by a variable lengthframe including logic channel information and performs conversionprocessing between fixed length cells for the exchange and a variablelength frame for the terminal, comprising frame production means forproducing a transmission frame based on data transmitted thereto fromthe terminal by way of a plurality of channels of the subscriber line,channel number to virtual path identifier information conversion meansfor converting a channel number or numbers of the subscriber line whichhave been used to transmit the transmission frame from the terminal intovirtual path identifier information as communication channel identifierinformation for the logic channel information sections of fixed lengthcells, data link connection identifier information to virtual channelidentifier information conversion means for converting data linkconnection identifier information as logic channel information to beadded to the transmission frame into virtual channel identifierinformation as the communication channel identifier information for thelogic channel information sections of fixed length cells, andtransmission frame disassembling means for disassembling thetransmission frame into fixed length cells to which the virtual pathidentifier information obtained by conversion by the channel number tovirtual path identifier information conversion means and the virtualchannel identifier information obtained by conversion by the data linkconnection identifier information to virtual channel identifierinformation conversion means are added and sending out the fixed lengthcells to the exchange, frame assembling means for assembling a call-inframe based on fixed length cells from the exchange designating theterminal as a destination of transmission, virtual channel identifierinformation to data link connection identifier information conversionmeans for converting virtual channel identifier information ascommunication channel identifier information for the logic channelinformation sections of the fixed length cells into data link connectionidentifier information as logic channel information to be added to thecall-in frame, virtual path identifier information to channel numberconversion means for converting virtual path identifier information asthe communication channel identifier information for the logic channelinformation sections of the fixed length cells into a channel number ornumbers of the subscriber line which are available upon transmission tothe terminal, and call-in frame disassembling means for transmitting thecall-in frame, to which the data link connection identifier informationobtained by conversion by the virtual channel identifier information todata link connection identifier information conversion means is added,by way of a channel or channels corresponding to the channel number ornumbers of the subscriber line obtained by conversion by the virtualpath identifier information to channel number conversion means to theterminal.

Preferably, the channel number to virtual path identifier informationconversion means and the virtual path identifier information to channelnumber conversion means commonly include first storage means for storingin advance a first corresponding relationship between the virtual pathidentifier information as the communication channel identifierinformation and the channel number or numbers of the subscriber linewhich are used between the terminal and the exchange, and the data linkconnection identifier information to virtual channel identifierinformation conversion means and the virtual channel identifierinformation to data link connection identifier information conversionmeans commonly include second storage means for storing in advance asecond corresponding relationship between the virtual channel identifierinformation as the communication channel identifier information and thedata link connection identifier to be added to a frame.

According to a yet further aspect of the present invention, there isprovided a call acceptance determination system for a fixed length cellhandling exchange in which one or more first terminals for use with adata communication method by fixed length cells each including a logicchannel information section and a data section and one or more secondterminals for use with another data communication method by a variablelength frame including logic channel information are accommodated by wayof respective subscriber lines, comprising, the exchange having aresource divided into a first terminal resource and a second terminalresource completely separate from each other, first terminal resourcecontrol means for controlling the first terminal resource and secondterminal resource control means for controlling the second terminalresource, the first terminal resource control means including fixedlength cell call acceptance determination means for determining whetheror not a fixed length cell call from one of the first terminals shouldbe accepted when the first terminal tries to use the first terminalresource, the second terminal resource control means including framecall acceptance determination means for determining whether or not aframe call from one of the second terminals should be accepted when thesecond terminal tries to use the second terminal resource.

The frame call acceptance determination means may include virtual bandcalculation means for multiplying a use requested band requested to setfrom one of the second terminals by a predetermined multiplexing rate tocalculate a use virtual band which is controlled by the network,subscriber line free band detection means for detecting a free band forthe subscriber lines for the second terminal, outgoing line free banddetection means for detecting a free band for the outgoing lines for thesecond terminal, first comparison means for comparing the use requestedband calculated by the virtual band calculation means and the free banddetected by the subscriber line free band detection means with eachother, second comparison means for comparing the use requested bandcalculated by the virtual band calculation means and the free banddetected by the outgoing line free band detection means with each other,and call acceptance means for accepting a frame call from one of thesecond terminals when the comparison by the first comparison meansproves that the use virtual band is smaller than the free band of thesubscriber lines for the second terminals and the comparison by thesecond comparison means proves that the use virtual band is smaller thanthe free band for the outgoing lines for the second terminal.

A use requested band requested to set from one of the second terminalsmay be added as band information to a frame call from the secondterminal and is transmitted to the virtual band calculation means of theframe call acceptance determination means together with the frame call.

The frame call acceptance determination means may include virtual bandsetting means for setting, when setting of a frame call is requestedfrom one of the second terminals, a physical maximum speed of the secondterminal as a use virtual band for the frame call, band assurancedetermination means for determining whether or not a band has beenassured already for a same sending subscriber as the second terminal,free band detection means for detecting a free band for the lines forthe second terminal, comparison means for comparing the use virtual bandset by the virtual band setting means and the free band detected by thefree band detection means with each other, and call acceptance means foraccepting, when the band assurance determination means determines that aband has been assured already for the same sending subscriber as thesecond terminal, the frame call from the second terminal unconditionallyand for assuring, when the band assurance determination means determinesthat no band has been assured as yet for the same sending subscriber asthe second terminal and the comparison by the comparison means provesthat the use virtual band is smaller than the free band for the linesfor the second terminal, the use virtual band and accepting the framecall from the second terminal.

According to a yet further aspect of the present invention, there isprovided a call acceptance determination system for a fixed length cellhandling exchange in which one or more first terminals for use with adata communication method by fixed length cells each including a logicchannel information section and a data section and one or more secondterminals for use with another data communication method by a variablelength frame including logic channel information are accommodated by wayof respective subscriber lines, comprising, the exchange having aresource shared commonly by the first terminals and the secondterminals, first terminal subscriber resource control means forcontrolling a first terminal subscriber access resource for a casewherein a fixed length cell call from one of the first terminals isinputted to the exchange by way of a corresponding one of the subscriberlines and then sent out to another one of the first terminals by way ofanother one of the subscriber lines, second terminal subscriber resourcecontrol means for controlling a second terminal subscriber accessresource for a case wherein a frame call from one of the secondterminals is inputted to the exchange by way of one of the subscriberlines and then sent out to another one of the second terminals by way ofanother one of the subscriber lines, and network resource control meansfor controlling a network common resource for a case wherein a fixedlength cell call from one of the first terminals or a frame call fromone of the second terminals is inputted to the exchange by way of acorresponding one of the subscriber lines and then sent out to a trunkline, the first terminal subscriber resource control means includingfixed length cell call acceptance determination means for determiningwhether or not a fixed length cell call from one of the first terminalsshould be accepted when the first terminal tries to use the firstterminal subscriber access resource, the second terminal resourcecontrol means including frame call acceptance determination means fordetermining whether or not a frame call from one of the second terminalsshould be accepted when the second terminal tries to use the secondterminal subscriber access resource, the network resource control meansincluding common resource call acceptance determination means fordetermining whether or not a fixed length cell call from one of thefirst terminals or a frame call from one of the second terminals shouldbe accepted when the first terminal or the second terminal tries to usethe network common resource.

The frame call acceptance determination means may include virtual bandcalculation means for multiplying a use requested band requested to setfrom one of the second terminals by a predetermined multiplexing rate tocalculate a use virtual band which is controlled by the network,incoming side subscriber line free band detection means for detecting afree band for the incoming side subscriber lines for the secondterminal, outgoing side subscriber line free band detection means fordetecting a free band for the outgoing side subscriber lines for thesecond terminal, first comparison means for comparing the use virtualband calculated by the virtual band calculation means and the free banddetected by the incoming side subscriber line free band detection meanswith each other, second comparison means for comparing the use virtualband calculated by the virtual band calculation means and the free banddetected by the outgoing side subscriber line free band detection meanswith each other, and call acceptance means for accepting a frame callfrom one of the second terminals when the comparison by the firstcomparison means proves that the use virtual band is smaller than thefree band for the incoming side subscriber lines for the second terminaland the comparison by the second comparison means proves that the usevirtual band is smaller than the free band for the outgoing sidesubscriber lines for the second terminal.

A use requested band requested to set from one of the second terminalsmay be added as band information to a frame call from the secondterminal and then transferred to the virtual band calculation means ofthe frame call acceptance determination means together with the framecall.

The common resource call acceptance determination means may includevirtual band calculation means for multiplying a use requested bandrequested to set from one of the first terminals or from one of thesecond terminals by a predetermined multiplexing rate to calculate a usevirtual band which is controlled by the network, common resource freeband detection means for detecting a free band on the network commonresource of the exchange, comparison means for comparing the use virtualband calculated by the virtual band calculation means and the free banddetected by the common resource free band detection means with eachother, and call acceptance means for accepting a fixed length cell callfrom one of the first terminals or a frame call from one of the secondterminals when the comparison by the comparison means proves that theuse virtual band is smaller than the free band on the network commonresource.

The predetermined multiplexing rate by which a use requested band ismultiplied by the virtual band calculation means may have two values setin advance including a first multiplexing rate for a use requested bandrequested to set from one of the first terminals and a secondmultiplexing rate for another use requested band requested to set fromone of the second terminals.

A use requested band requested to set from one of the second terminalsmay be added as band information to a frame call from the secondterminal and then transferred to the virtual band calculation means ofthe common resource call acceptance determination means together withthe frame call.

The common resource call acceptance determination means may includecommon resource fixed length cell call acceptance determination meansfor determining whether or not a fixed length cell call from one of thefirst terminals should be accepted when the first terminal tries to usethe network common resource, and common resource frame call acceptancedetermination means for determining whether or not a frame call from oneof the second terminals should be accepted when the second terminaltries to use the network common resource.

The common resource frame call acceptance determination means mayinclude virtual band setting means for setting, when setting of a framecall is requested from one of the second terminals, a physical maximumspeed of the second terminal as a use virtual band for the frame call,band assurance determination means for determining whether or not a bandhas been assured already for a same sending subscriber as the secondterminal on the network common resource, common resource free banddetection means for detecting a free band on the network common resourceof the exchange, comparison means for comparing the use virtual band setby the virtual band setting means and the free band detected by thecommon resource free band detection means with each other, and callacceptance means for accepting, when the band assurance determinationmeans determines that a band has been assured already for the samesending subscriber as the second terminal, the frame call from thesecond terminal unconditionally and for assuring, when the bandassurance determination means determines that no band has been assuredas yet for the same sending subscriber as the second terminal and thecomparison by the comparison means proves that the use virtual band issmaller than the free band on the network common resource, the usevirtual band and accepting the frame call from the second terminal.

Alternatively, the common resource frame call acceptance determinationmeans may include virtual band setting means for setting a use requestedband requested to set for a frame call from one of the second terminalsas a use virtual band for the frame call, band assurance determinationmeans for determining whether or not a band has been assured already fora same sending subscriber as the second terminal on the network commonresource, common resource free band detection means for detecting a freeband on the network common resource of the exchange, first comparisonmeans for comparing, when the band assurance determination meansdetermines that no band has been assured as yet for the same sendingsubscriber as the second terminal, the use virtual band set by thevirtual band setting means and the free band detected by the commonresource free band detection means with each other, assured bandextraction means for extracting, when the band assurance determinationmeans determines that a band has been assured for the same sendingsubscriber as the second terminal, the band assured already for thesecond terminal, second comparison means for comparing the bandextracted by the assured band extraction means and a physical maximumspeed of the second terminal with each other, third comparison means forcomparing, when the comparison by the second comparison means provesthat the band extracted by the assured band extraction means is equal toor lower than the physical maximum speed of the second terminal, a sumof the band extracted by the assured band extraction means and the usevirtual band set by the virtual band setting means and the physicalmaximum speed of the second terminal with each other, remainingavailable band calculation means for subtracting, when the comparison bythe third comparison means proves that the sum is higher than thephysical maximum speed of the second terminal, the band extracted by theassured band extraction means from the physical maximum speed of thesecond terminal to calculate a remaining available band, fourthcomparison means for comparing the remaining available band calculatedby the remaining available band calculation means and the free banddetected by the common resource free band detection means with eachother, fifth comparison means for comparing, when the comparison by thethird comparison means proves that the sum is equal to of lower than thephysical maximum speed of the second terminal, the use virtual band setby the virtual band setting means and the free band detected by thecommon resource free band detection means with each other, and callacceptance means for assuring, when the comparison by the firstcomparison means or the fifth comparison means proves that the usevirtual band is smaller than the free band on the common resource, theuse virtual band and accepting the frame call from the second terminal,for assuring, when the comparison by the fourth comparison means provesthat the remaining available band is smaller than the free band on thecommon resource, the remaining available band and accepting the framecall from the second terminal, and for accepting, when the comparison bythe second comparison means proves that the band extracted by theassured band extraction means is higher than the physical maximum speedof the second terminal, the frame call from the second terminalunconditionally.

The call acceptance determination system may be constructed such that,for each of the second terminals connected to the exchange by way of therespective subscriber lines, a use band table is provided forcontrolling and storing a physical maximum speed of the second terminaland a sum total of use requested bands which have been requested to setbefore the present point of time by the second terminal, and the assuredband extraction means extracts the sum total of the use requested bandsof the use band table as a band assured already for the second terminalwhereas the physical maximum speed of the second terminal which is to beused by the second comparison means, the third comparison means and theremaining available band calculation means is read out from the use bandtable.

A use requested band requested to set from one of the second terminalsmay be added as band information to a frame call from the secondterminal and then transferred to the virtual band setting means of thecommon resource frame call acceptance determination means together withthe frame call.

With the variable length frame exchanging method by a fixed length cellhandling exchange and the variable length frame exchanging interfaceapparatus of the present invention described above, the followingeffects and/or advantages can be achieved.

1. A frame having a variable data length can be exchanged at a highspeed by the fixed length cell handling exchange.

2. Since a predetermined corresponding relationship is provided betweena used channel number upon communication of a variable length frame anddata link connection identifier information and communication channelidentifier information of a destination of transmission, a hard logicrouting function can be provided, and when it is tried to accommodate avariable length frame terminal into the fixed length cell handlingexchange, assembly and/or disassembly of a cell or routing on hardwarefor a variable length frame can be realized readily.

3. Since a cell relay between different fixed length cell handlingexchanges is the same as in ordinary fixed length cell handlingexchange, there is no need of particularly getting aware of a variablelength frame, and a variable length frame terminal can be accommodatedinto a fixed length cell handling exchange using an existing techniqueas it is. Further, a service of accommodating and connecting a variablelength frame terminal into and to a fixed length cell handling exchangecan be realized as one of services of the fixed length cell handlingexchange.

Further, with the call acceptance determination system for a fixedlength cell handling exchange of the present invention, the followingeffects and/or advantages can be achieved.

4. By dividing the resource of a fixed length cell handling exchangesimply, control of the first terminal resource and call acceptancedetermination can be processed completely independently of control ofthe second terminal resource and call acceptance determination, and afirst terminal and a second terminal can be accommodated very readilyinto the same exchange and a service of accommodating and connecting asecond terminal into and to the fixed length cell handling exchange canbe realized as one of services of the fixed length cell handlingexchange.

5. Since control of the first terminal subscriber access resource andcall acceptance determination and control of the second terminalsubscriber access resource and call acceptance determination areperformed by the fixed length cell call acceptance determination meansand the frame call acceptance determination means, respectively, andcontrol of the network common resource and call acceptance determinationare performed by the common resource call acceptance determinationmeans, even where the resource of the fixed length cell handlingexchange is shared commonly for the first terminals and the secondterminals, a first terminal and a second terminal can be accommodatedvery readily into the same ATM exchange, and a service of accommodatingand connecting a second terminal into and to the fixed length cellhandling exchange can be realized as one of services of the fixed lengthcell handling exchange.

6. Since a use requested band is added as band information to a fixedlength cell call or a frame call, a user of a second terminal need notany more report a use requested band every time before a call isdeveloped, and further enhancement in service can be achieved.

7. Since at least one path from a certain second terminal is set on thelines, a band for a physical maximum speed is assured whereas a bandhigher than the physical maximum speed is not assured, and consequently,a contract for a speed higher than the physical maximum speed can beallowed for each of the second terminals. Then, when a second terminalis accommodated into the fixed length cell handling exchange so as tooffer a service, a path for the variable length frame can be set to thefixed length cell handling switched network in the same conditions asthe existing services and besides effective utilization of the resourcecan be realized.

8. Since call acceptance determination processing is performed using thefirst and second multiplexing rates conforming to characteristics of afixed length cell call and a frame call and the common resource callacceptance determination means is divided into the common resource fixedlength cell call acceptance determination means and the common resourceframe call acceptance determination means, call acceptance determinationprocessing can be performed in accordance with separate algorithms for afixed length cell call from a first terminal and a frame call from asecond terminal on the network common resource, and by assuring a bandfor paths for all of the second terminals as a virtual band, effectiveutilization of the common resource can be realized.

9. By performing call acceptance determination processing such that,when the sum total of use requested bands requested to set from a secondterminal before the present point of time is lower than the physicalmaximum speed, a band is assured with the sum total of use requestedbands, but when the sum total of use requested bands exceeds thephysical maximum speed, a band is assured with the physical maximumspeed, the common resource of the fixed length cell handling exchangecan be utilized further effectively.

10. Since the physical maximum speed and the sum total of use requestedbands requested to set before the present point of time are controlledand stored by means of the use band table for each second terminal, thesum total of use requested bands of the use band table can be used as anassured band of the second terminal, and besides, the physical maximumspeed of the second terminal which is required for various comparisonprocessing or for calculation processing of a remaining available bandcan be read out from the use band table and used for such processing.Consequently, control of various data and calculation processing ofvarious means can be performed efficiently.

Further objects, features and advantages of the present invention willbecome apparent from the following detailed description when read inconjunction with the accompanying drawings in which like parts orelements are denoted by like reference characters.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 4 are block diagrams illustrating different aspects of thepresent invention;

FIG. 5 is a block diagram of a variable length frame exchanginginterface apparatus showing a first preferred embodiment of the presentinvention;

FIG. 6 is a block diagram showing details of a DS1 interface section of-the variable length frame exchanging interface apparatus shown in FIG.5;

FIG. 7 is a block diagram showing details of a frame processing sectionof the variable length frame exchanging interface apparatus shown inFIG. 5;

FIG. 8 is a block diagram showing details of an optical interfacesection of the variable length frame exchanging interface apparatusshown in FIG. 5;

FIG. 9 is a block diagram functionally illustrating those elements ofthe variable length frame exchanging interface apparatus shown in FIG. 5which perform their processing functions upon transmission of data froma frame relay terminal to an ATM network;

FIG. 10 is a block diagram functionally illustrating those elements ofthe variable length frame exchanging interface apparatus shown in FIG. 5which performs their processing functions upon transmission of data fromthe ATM network to a frame relay terminal;

FIG. 11 is a table illustrating a mapping relationship between a channelnumber/DLCI and a VPI/VCI in the variable length frame exchanginginterface apparatus shown in FIG. 5;

FIG. 12 is a table illustrating a mapping relationship between a channelnumber and a VPI in the variable length frame exchanging interfaceapparatus shown in FIG. 5;

FIG. 13 is a table illustrating a mapping relationship between a DLCIand a VCI in the variable length frame exchanging interface apparatusshown in FIG. 5;

FIG. 14 is a diagrammatic view illustrating a mapping relationshipbetween a link (channel number/DLCI) of a frame relay and communicationchannel identifier information (VPI/VCI) of an ATM cell in the variablelength frame exchanging interface apparatus shown in FIG. 5;

FIG. 15 is a diagrammatic view illustrating a relationship between aframe relay packet and an ATM cell in the variable length frameexchanging interface apparatus shown in FIG. 5;

FIG. 16 is a table showing a memory for controlling a channelcombination pattern and illustrating operation of the variable lengthframe exchanging interface apparatus shown in FIG. 5;

FIG. 17 is a table showing a memory for controlling a relationshipbetween a frame and a cell and illustrating operation of the variablelength frame exchanging interface apparatus shown in FIG. 5;

FIG. 18 is a block diagram of an ATM exchange system showing a secondpreferred embodiment of the present invention;

FIG. 19 is a block diagram illustrating a functional construction offrame relay call acceptance determination means of the ATM exchangesystem shown in FIG. 18;

FIG. 20 is a flow chart illustrating operation of the frame relay callacceptance determination means shown in FIG. 19;

FIG. 21 is a block diagram showing a modified ATM exchange system to theATM exchange system of FIG. 18 which additionally includes a signalapparatus;

FIG. 22 is a diagram illustrating a sequence of processing when callconnection is requested from an ATM terminal of the ATM exchange systemshown in FIG. 21;

FIG. 23 is a diagram illustrating a sequence of processing when callconnection is requested from a frame relay terminal of the ATM exchangesystem shown in FIG. 21;

FIG. 24 is a block diagram illustrating a functional construction offrame relay call acceptance determination means showing a thirdpreferred embodiment of the present invention;

FIG. 25 is a diagrammatic view illustrating an example of a state ofpaths when a frame relay terminal is accommodated in an actual ATMexchange terminal;

FIG. 26 is a flow chart illustrating operation of the frame relay callacceptance determination means shown in FIG. 24;

FIG. 27 is a diagrammatic view showing tables for band assurancedetermination employed in the frame relay call acceptance determinationmeans shown in FIG. 24;

FIG. 28 is a block diagram of another ATM exchange system showing afourth preferred embodiment of the present invention;

FIG. 29 is a block diagram illustrating a functional construction offrame relay call acceptance determination means of the ATM exchangesystem shown in FIG. 28;

FIG. 30 is a block diagram illustrating a functional construction ofcommon resource call acceptance determination means of the ATM exchangesystem shown in FIG. 28;

FIG. 31 is a flow chart illustrating operation of the frame relay callacceptance determination means shown in FIG. 29;

FIG. 32 is a flow chart illustrating operation of the common resourcecall acceptance determination means shown in FIG. 30;

FIG. 33 is a block diagram of a further ATM exchange system showing afifth preferred embodiment of the present invention;

FIG. 34 is a flow chart illustrating operation of common resource ATMcall acceptance determination means of the ATM exchange system shown inFIG. 33;

FIG. 35 is a flow chart illustrating operation of common resource framerelay call acceptance determination means of the ATM exchange systemshown in FIG. 33;

FIG. 36 is a block diagram showing a functional construction of commonresource frame relay call acceptance determination means of a stillfurther ATM exchange system showing a sixth preferred embodiment of thepresent invention;

FIG. 37 is a flow chart illustrating operation of the common resourceframe relay call acceptance determination means shown in FIG. 36;

FIG. 38 is a block diagram showing a functional construction of commonresource frame relay call acceptance determination means of a yetfurther ATM exchange system showing a seventh preferred embodiment ofthe present invention;

FIG. 39 is a flow chart illustrating operation of the common resourceframe relay call acceptance determination means shown in FIG. 38;

FIG. 40 is a diagrammatic view showing used band tables employed in thecommon resource frame relay call acceptance determination means shown inFIG. 38;

FIG. 41 is a diagrammatic view illustrating band assurance in allocationwithin a physical maximum speed in the common resource frame relay callacceptance determination means shown in FIG. 38;

FIG. 42 is a diagrammatic view illustrating a condition of a used bandtable illustrated in FIG. 40 before acceptance of a predetermined line;

FIG. 43 is a similar view but illustrating a condition of another usedband table illustrated in FIG. 40 before acceptance of another line; and

FIG. 44 is a block diagram showing an example for reference of a systemwherein an ISDN frame relay is used to interconnect a plurality of LANs.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

a. Different Aspects of the Invention

FIG. 1 illustrates an aspect of the present invention. Referring to FIG.1, a sending side frame relay terminal 101 and a receiving side framerelay terminal 102 are used for a data communication method by avariable length frame (hereinafter referred to as frame relay packet)including logic channel information and are connected to an ATM switchednetwork (ATM exchange) 103, which handles fixed length cells(hereinafter referred to as ATM cells) each including a logic channelinformation section and a data section, by way of subscriber lines 104and 105, respectively, each having at least one channel.

A sending side frame relay exchanging interface apparatus (variablelength frame exchanging interface apparatus) 110 is interposed in thesubscriber line 104 and performs sending conversion processing betweenATM cells for the ATM switched network 103 and a frame relay packet forthe frame relay terminal 101 in order to realize the variable lengthframe exchanging method of the present invention.

A receiving side frame relay exchanging interface apparatus (variablelength frame exchanging interface apparatus) 120 is interposed in thesubscriber line 105 and performs receiving conversion processing betweenATM cells for the ATM switched network 103 and a frame relay packet forthe frame relay terminal 102 in order to realize the variable lengthframe exchanging method of the present invention.

The sending side frame relay exchanging interface apparatus 110 includesframe relay packet production means (frame production means) 111,channel number to virtual path identifier (channel number/virtual pathidentifier) information conversion means 112, data link connectionidentifier information to virtual channel identifier information (datalink connection identifier information/virtual channel identifierinformation) conversion means 113, and transmission frame relay packetdisassembling means (transmission frame disassembling means) 114.

The frame relay packet production means 111 produces a transmissionframe relay packet based on data transmitted thereto from the framerelay terminal 101 by way of a plurality of channels of the subscriberline 104. The channel number to virtual path identifier informationconversion means 112 converts a channel number or numbers of thesubscriber line 104 which have been used to transmit the transmissionframe relay packet from the frame relay terminal 101 into virtual pathidentifier information as ATM communication channel identifierinformation of the logic channel information sections of ATM cells.

The data link connection identifier information to virtual channelidentifier information conversion means 113 converts data linkconnection identifier information as logic channel information to beadded to the transmission frame relay packet into virtual channelidentifier information as the ATM communication channel identifierinformation of the logic channel information sections of ATM cells. Thetransmission frame relay packet disassembling means 114 disassembles thetransmission frame relay packet into ATM cells to which the virtual pathidentifier information obtained by conversion by the channel number tovirtual path identifier information conversion means 112 and the virtualchannel identifier information obtained by conversion by the data linkconnection identifier information to virtual channel identifierinformation conversion means 113 are added, and sends out the ATM cellsto the ATM switched network 103.

The channel number to virtual path identifier information conversionmeans 112 includes storage means 115 for storing in advance acorresponding relationship between a channel number or numbers of thesubscriber line 104 which are used between the frame relay terminal 101and the ATM switched network 103 and virtual path identifier informationas ATM communication channel identifier information, and the data linkconnection identifier information to virtual channel identifierinformation conversion means 113 includes another storage means 116 forstoring in advance another relationship between a data link connectionidentifier to be added to a frame relay packet and virtual channelidentifier information as the ATM communication channel identifierinformation.

Meanwhile, the receiving side frame relay exchanging interface apparatus120 includes frame relay packet assembling means (frame assemblingmeans) 121, virtual channel identifier information to data linkconnection identifier information conversion means 122, virtual pathidentifier information to channel number conversion means 123, andcall-in frame relay packet disassembling means (call-in framedisassembling means) 124.

The frame relay packet assembling means 121 assembles a call-in framerelay packet based on ATM cells from the ATM switched network 103designating the frame relay terminal 102 as a destination oftransmission. The virtual channel identifier information to data linkconnection identifier information conversion means 122 converts virtualchannel identifier information as ATM communication channel identifierinformation of the logic channel information sections of the ATM cellsinto data link connection identifier information as logic channelinformation to be added to the call-in frame relay packet.

The virtual path identifier information to channel number conversionmeans 123 converts virtual path identifier information as the ATMcommunication channel identifier information of the logic channelinformation sections of the ATM cells into a channel number or numbersof the subscriber line 105 which are available upon transmission to theframe relay terminal 102. The call-in frame relay packet disassemblingmeans 124 transmits the call-in frame relay packet, to which the datalink connection identifier information obtained by conversion by thevirtual channel identifier information to data link connectionidentifier information conversion means 122 is added, by way of achannel or channels corresponding to the channel number or numbers ofthe subscriber line 105 obtained by conversion by the virtual pathidentifier information to channel number conversion means 123 to theframe relay terminal 102.

The virtual path identifier information to channel number conversionmeans 123 includes storage means 125 for storing in advance acorresponding relationship between virtual path identifier informationas the ATM communication channel identifier information and a channelnumber or numbers of the subscriber line 105 which are used between theframe relay terminal 102 and the ATM switched network 103, and thevirtual channel identifier information to data link connectionidentifier information conversion means 122 includes another storagemeans 126 for storing in advance another relationship between virtualchannel identifier information as the ATM communication channelidentifier information and a data link connection identifier to be addedto a frame relay packet.

Due to the construction described above, in the sending side frame relayinterface apparatus 110, when a transmission frame relay packet (withthe frame relay terminal 102 designated as a destination oftransmission) is received from the frame relay terminal 101 by way ofthe subscriber line 104, the frame relay packet production means 111first produces a transmission frame relay packet once based on the datatransmitted thereto from the frame relay terminal 101 by way of aplurality of channels of the subscriber line 104.

Then, a channel number or numbers of the subscriber line 104 which havebeen used to transmit the transmission frame relay packet from the framerelay terminal 101 is converted into virtual path identifier informationin accordance with the corresponding relationship of the storage means115 by the channel number to virtual path identifier informationconversion means 112, and data link connection identifier information tobe added to the transmission frame relay packet is converted intovirtual channel identifier information based on the correspondingrelationship of the storage means 116 by the data link connectionidentifier information to virtual channel identifier informationconversion means 113.

Thereafter, the transmission frame relay packet produced by the framerelay packet production means 111 is disassembled by the transmissionframe relay packet disassembling means 114 into ATM cells to which thevirtual path identifier information obtained by conversion by thechannel number to virtual path identifier information conversion means112 and the virtual channel identifier information obtained byconversion by the data link connection identifier information to virtualchannel identifier information conversion means 113 are added, and isthen sent out to the ATM switched network 103. Consequently, the framerelay packet from the frame relay terminal 101 is exchanged as the ATMcells in accordance with the virtual path identifier information and thevirtual channel identifier information by the ATM switched network 103so that it is transmitted to the frame relay terminal 102.

Meanwhile, in the receiving side frame relay exchanging interfaceapparatus 120, when ATM cells designating the frame relay terminal 102as a destination of transmission are outputted from the ATM switchednetwork 103 to the subscriber line 105, the frame relay packetassembling means 121 assembles a call-in frame relay packet based on theATM cells from the ATM switched network 103 designating the frame relayterminal 102 as a destination of transmission.

Then, virtual channel identifier information to be added to each of theATM cells is converted into data link connection identifier informationbased on the corresponding relationship of the storage means 126 by thevirtual channel identifier information to data link connectionidentifier information conversion means 122, and virtual path identifierinformation to be added to each of the ATM cells is converted into achannel number or numbers of the subscriber line 105, which areavailable upon transmission to the frame relay terminal 102, based onthe corresponding relationship of the storage means 125 by the virtualpath identifier information to channel number conversion means 123.

Thereafter, the call-in frame relay packet, which has been assembled bythe frame relay packet assembling means 121 and to which the data linkconnection identifier information obtained by conversion by the virtualchannel identifier information to data link connection identifierinformation conversion means 122 is added, is disassembled by thecall-in frame relay packet disassembling means 124 and transmitted byway of a channel or channels corresponding to a channel number ornumbers of the subscriber line 105 obtained by conversion by the virtualpath identifier information to channel number conversion means 123 tothe frame relay terminal 102.

FIG. 2 illustrates another aspect of the present invention. Referring toFIG. 2, a frame relay terminal 100 is used for a data communicationmethod by a variable length frame (hereinafter referred to as framerelay packet) including logic channel information and is connected to anATM switched network (ATM exchange) 103, which handles fixed lengthcells (hereinafter referred to as ATM cells) each including a logicchannel information section and a data section, by way of a subscriberline 106 having at least one channel.

A frame relay exchanging interface apparatus (variable length frameexchanging interface apparatus) 130 is interposed in the subscriber line106 and performs conversion processing between ATM cells for the ATMswitched network 103 and a frame relay packet for the frame relayterminal 100 in order to realize the variable length frame exchangingmethod of the present invention. The frame relay exchanging interfaceapparatus 130 has both of the function of the sending side frame relayexchanging interface apparatus 110 and the function of the receivingside frame relay exchanging interface apparatus 120 describedhereinabove with reference to FIG. 1.

In particular, the frame relay exchanging interface apparatus 130comprises frame relay packet production means (frame production means)131, channel number to virtual path identifier information conversionmeans 132, data link connection identifier information to virtualchannel identifier information conversion means 133, transmission framerelay packet disassembling means (transmission frame disassemblingmeans) 134, frame relay packet assembling means (frame assembling means)135, virtual channel identifier information to data link connectionidentifier information conversion means 136, virtual path identifierinformation to channel number conversion means 137, and call-in framerelay packet disassembling means (call-in frame disassembling means)138.

The frame relay packet production means 131 produces a transmissionframe relay packet based on data transmitted thereto from the framerelay terminal 100 by way of a plurality of channels of the subscriberline 106. The channel number to virtual path identifier informationconversion means 132 converts a channel number or numbers of thesubscriber line 106 which have been used to transmit the transmissionframe relay packet from the frame relay terminal 100 into virtual pathidentifier information as ATM communication channel identifierinformation of the logic channel information sections of ATM cells.

The data link connection identifier information to virtual channelidentifier information conversion means 133 converts data linkconnection identifier information as logic channel information to beadded to the transmission frame relay packet into virtual channelidentifier information as the ATM communication channel identifierinformation of the logic channel information sections of ATM cells. Thetransmission frame relay packet disassembling means 134 disassembles thetransmission frame relay packet into ATM cells to which the virtual pathidentifier information obtained by conversion by the channel number tovirtual path identifier information conversion means 132 and the virtualchannel identifier information obtained by conversion by the data linkconnection identifier information to virtual channel identifierinformation conversion means 133 are added, and sends out the ATM cellsto the ATM switched network 103.

The frame relay packet assembling means 135 assembles a call-in framerelay packet based on ATM cells from the ATM switched network 103designating the frame relay terminal 100 as a destination oftransmission. The virtual channel identifier information to data linkconnection identifier information conversion means 136 converts virtualchannel identification as ATM communication channel identifierinformation of the logic channel information sections of ATM cells intodata link connection identifier information as logic channel informationto be added to the call-in frame relay packet.

The virtual path identifier information to channel number conversionmeans 137 converts virtual path identifier information as the ATMcommunication channel identifier information of the logic channelinformation sections of ATM cells into a channel number or numbers ofthe subscriber line 106 which are available upon transmission to theframe relay terminal 100. The call-in frame relay packet disassemblingmeans 138 transmits the call-in frame relay packet, to which the datalink connection identifier information obtained by conversion by thevirtual channel identifier information to data link connectionidentifier information conversion means 136 is added, by way of achannel or channels corresponding to the channel number or numbers ofthe subscriber line 106 obtained by conversion by the virtual pathidentifier information to channel number conversion means 137 to theframe relay terminal 100.

The channel number to virtual path identifier information conversionmeans 132 and the virtual path identifier information to channel numberconversion means 137 commonly include first storage means 139 forstoring in advance a first corresponding relationship between thevirtual path identifier information as the ATM communication channelidentifier information and the channel number or numbers of thesubscriber line 106 which are used between the frame relay terminal 100and the ATM switched network 103, and the data link connectionidentifier information to virtual channel identifier informationconversion means 133 and the virtual channel identifier information todata link connection identifier information conversion means 136commonly include second storage means 140 for storing in advance asecond corresponding relationship between the virtual channel identifierinformation as the ATM communication channel identifier information andthe data link connection identifier to be added to a frame relay packet.

In the frame relay interface apparatus 130 having the constructiondescribed above, when a transmission frame relay packet is transmittedthereto from the frame relay terminal 101 by way of the subscriber line106, a transmission frame relay packet is produced once based on thedata transmitted thereto from the frame relay terminal 100 by way of aplurality of channels of the subscriber line 106 by the frame relaypacket production means 131.

Then, a channel number or numbers of the subscriber line 106 which havebeen used to transmit the transmission frame relay packet from the framerelay terminal 100 is converted into virtual path identifier informationby the channel number to virtual path identifier information conversionmeans 132, and data link connection identifier information to be addedto the transmission frame relay packet is converted into virtual channelidentifier information by the data link connection identifierinformation to virtual channel identifier information conversion means133.

Thereafter, the transmission frame relay packet produced by the framerelay packet production means 131 is disassembled by the transmissionframe relay packet disassembling means 134 into ATM cells to which thevirtual path identifier information obtained by conversion by thechannel number to virtual path identifier information conversion means132 and the virtual channel identifier information obtained byconversion by the data link connection identifier information to virtualchannel identifier information conversion means 133 are added, and thensent out to the ATM switched network 103. Consequently, the frame relaypacket from the frame relay terminal 100 is exchanged as the ATM cellsin accordance with the virtual path identifier information and thevirtual channel identifier information by the ATM switched network 103.

On the other hand, when ATM cells with the frame relay terminal 100designated as a destination of transmission are outputted from the ATMswitched network 103 to the subscriber line 106, a call-in frame relaypacket is first assembled by the frame relay packet assembling means 135based on the ATM cells from the ATM switched network 103 designating theframe relay terminal 100 as a destination of transmission.

Then, virtual channel identification to be added to the ATM cells isconverted into data link connection identifier information by thevirtual channel identifier information to data link connectionidentifier information conversion means 136, and virtual path identifierinformation to be added to the ATM cells is converted into a channelnumber or numbers of the subscriber line 106, which are available upontransmission to the frame relay terminal 100, by the virtual pathidentifier information to channel number conversion means 137.

Thereafter, the call-in frame relay packet, which has been assembled bythe frame relay packet assembling means 135 and to which the data linkconnection identifier information obtained by conversion by the virtualchannel identifier information to data link connection identifierinformation conversion means 136 is added, is disassembled by thecall-in frame relay packet disassembling means 138 and transmitted tothe frame relay terminal 100 by way of a channel or channelscorresponding to a channel number or numbers of the subscriber line 106obtained by conversion by the virtual path identifier information tochannel number conversion means 137.

Here, the first corresponding relationship between the virtual pathidentifier information and the channel number or numbers of thesubscriber line 106 which are used between the frame relay terminal 100and the ATM switched network 103 and the second correspondingrelationship between the virtual channel identifier information and thedata link connection identifier to be added to a frame relay packet arestored in advance in the first storage means 139 and the second storagemeans 140, respectively.

Accordingly, the conversion processing by the channel number to virtualpath identifier information conversion means 132 and the virtual pathidentifier information to channel number conversion means 137 isperformed based on the first corresponding relationship of the firststorage means 139 while the conversion processing by the data linkconnection identifier information to virtual channel identifierinformation conversion means 133 and the virtual channel identifierinformation to data link connection identifier information conversionmeans 136 is performed based on the second corresponding relationship ofthe second storage means 140.

FIG. 3 illustrates a further aspect of the present invention. Referringto FIG. 3, an ATM exchange 200 handles fixed length cells each includinga logic channel information section and a data section and accommodatesone or more ATM terminals 201 as first terminals for use with the datacommunication method by fixed length cells (hereinafter referred to asATM cells) described hereinabove by way of respective ATM terminalsubscriber lines 203. The ATM exchange 200 further accommodates one ormore frame relay terminals 202 as second terminals for use with the datacommunication method by a variable length frame (hereinafter referred toas frame relay packet) including logic channel information by way ofrespective frame relay terminal subscriber lines 204.

The ATM exchange 200 has a resource (free band) divided into an ATMterminal resource (first terminal resource) and a frame relay terminalresource (second terminal resource) completely separate from each other.Accordingly, also the trunk lines of the ATM exchange 200 are completelyseparated into ATM terminal trunk lines 205 and frame relay terminaltrunk lines 206.

In the present aspect of the invention. ATM terminal resource controlmeans (first terminal resource control means) 207 for controlling theATM terminal resource and frame relay terminal resource control means(second terminal resource control means) 208 for controlling the framerelay terminal resource are provided. Here, the ATM terminal resourcecontrol means 207 includes ATM call acceptance determination means(fixed length cell call acceptance determination means) 209 fordetermining whether or not an ATM call (fixed length cell call) from oneof the ATM terminals 201 should be accepted when the ATM terminal 201tries to use the ATM terminal resource, and the frame relay terminalresource control means 208 includes frame relay call acceptancedetermination means (frame call acceptance determination means) 210 fordetermining whether or not a frame relay call (frame call) from one ofthe frame relay terminals 202 should be accepted when the frame relayterminal 202 tries to use the frame relay terminal resource.

The frame relay call acceptance determination means 210 may includevirtual band calculation means for multiplying a use requested bandrequested to set from one of the frame relay terminals 202 by apredetermined multiplexing rate α to calculate a use virtual band A1which is controlled by the network, subscriber line free band detectionmeans for detecting a free band B1 for the subscriber lines 204 for theframe relay terminal, outgoing line free band detection means fordetecting a free band C1 for the outgoing lines (subscriber lines 204 ortrunk lines 206) for the frame relay terminal, first comparison meansfor comparing the use requested band A1 calculated by the virtual bandcalculation means and the free band B1 detected by the subscriber linefree band detection means with each other, second comparison means forcomparing the use requested band A1 calculated by the virtual bandcalculation means and the free band C1 detected by the outgoing linefree band detection means with each other, and call acceptance means foraccepting a frame relay call from one of the frame relay terminals 202when the result of comparison by the first comparison means is [freeband B1 for the subscriber line 204 for the frame relay terminal]>[usevirtual band A1] and the result of comparison by the second comparisonmeans is [free band C1 for the outgoing lines for the frame relayterminal]>[use virtual band A1].

A use requested band requested to set from one of the frame relayterminals 202 may be added as band information to a frame relay callfrom the frame relay terminal 202 and transmitted to the virtual bandcalculation means of the frame relay call acceptance determination means210 together with the frame relay call.

Alternatively, the frame relay call acceptance determination means 210may include virtual band setting means for setting, when setting of aframe relay call is requested from one of the frame relay terminals 202,a physical maximum speed (physical line speed) of the frame relayterminal 202 as a use virtual band A2 for the frame relay call, bandassurance determination means for determining whether or not a band hasbeen assured already for a same sending subscriber as the frame relayterminal 202, free band detection means for detecting a free band B2 forthe frame relay terminal lines 204 and 206 for the frame relay terminal,comparison means for comparing the use virtual band A2 set by thevirtual band setting means and the free band B2 detected by the freeband detection means with each other, and call acceptance meansdescribed below.

In particular, the call acceptance means employed here accepts, when theband assurance determination means determines that a band has beenassured already for the same sending subscriber as the frame relayterminal 202, the frame relay call from the frame relay terminal 202unconditionally, but assures, when the band assurance determinationmeans determines that no band has been assured as yet for the samesending subscriber as the frame relay terminal 202 and the result ofcomparison by the comparison means is [free band B2 for the frame relayterminal lines 204 and 206 for the frame relay terminal]>[use virtualband A2], the use virtual band A2 and accepts the frame relay call fromthe frame relay terminal 202.

In the system described above, the ATM terminal resource and the framerelay terminal resource are set completely separate from each other onthe resource of the ATM exchange 200 and are controlled by the ATMterminal resource control means 207 and the frame relay terminalresource control means 208, respectively.

When an ATM terminal 201 tries to use the ATM terminal resource, the ATMcall acceptance determination means 209 determines whether or not theATM call from the ATM terminal 201 should be accepted, but when a framerelay terminal 202 tries to use the frame relay terminal resource, theframe relay call acceptance determination means 210 determines whetheror not the frame relay call from the frame relay terminal 202 should beaccepted.

Since the resource of the ATM exchange 200 is divided simply in thismanner, control of the resource for and call acceptance determination ofan ATM terminal 201 and control of the resource for and call acceptancedetermination of a frame relay terminal 202 can be processed completelyindependently of each other, and consequently, the ATM terminals 201 andthe frame relay terminals 202 can be accommodated into the same ATMexchange 200.

In this instance, the frame relay call acceptance determination means210 multiplies the use requested band requested to set from the framerelay terminal 202 by the predetermined multiplexing rate α to calculatea use virtual band A1 which is controlled by the network, supervises afree band B1 for the subscriber lines 204 for the frame relay terminaland a free band C1 for the outgoing lines (subscriber lines 204 or trunklines 206) for the frame relay terminal, and accepts the frame relaycall from the frame relay terminal 202 in the case of [free band B1 forthe subscriber lines 204 for the frame relay terminal]>[use virtual bandA1] and [free band C1 for the outgoing lines for the frame relayterminal]>[use virtual band A1].

In this instance, if the use requested band requested to set from theframe relay terminal 202 is transferred as band information togetherwith the frame relay call to the virtual band calculation means of theframe relay call acceptance determination means 210, then the user ofthe frame relay terminal 202 need not any more report a use requestedband every time before a call is developed.

Alternatively, the frame relay call acceptance determination means 210may set, when setting of a frame relay call is requested from one of theframe relay terminals 202, a physical maximum speed (physical linespeed) of the frame relay terminal 202 as a use virtual band A2 for theframe relay call, supervise a free band B2 for the frame relay terminallines 204 and 206, and accept, when a band has been assured already forthe same sending subscriber as the frame relay terminal 202, the framerelay call from the frame relay terminal 202 unconditionally, butassure, when no band has been assured as yet for the same sendingsubscriber as the frame relay terminal 202 and the free band B2 for theframe relay terminal lines 204 and 206 for the frame relay terminal isgreater than the use virtual band A2, the use virtual band A2 and acceptthe frame relay call from the frame relay terminal 202.

FIG. 4 illustrates a still further aspect of the present invention.Referring to FIG. 4, also in the present aspect of the invention, an ATMexchange 200 handles fixed length cells each including a logic channelinformation section and a data section and accommodates one or more ATMterminals 201 as first terminals for use with the data communicationmethod by fixed length cells (hereinafter referred to as ATM cells)described hereinabove by way of respective ATM terminal subscriber lines203 as well as one or more frame relay terminals 202 as second terminalsfor use with the data communication system by a variable length frame(hereinafter referred to as frame relay packet) including logic channelinformation by way of respective frame relay terminal subscriber lines204. However, in the present aspect of the invention, the ATM exchange200 has a resource (free band) shared commonly by the ATM terminals andthe frame relay terminals, and the trunk lines 211 of the ATM exchange200 are not separated for the ATM terminals and the frame relayterminals.

Further, according to the present aspect of the invention. ATM terminalsubscriber resource control means (first terminal subscriber resourcecontrol means) 212 for controlling an ATM terminal subscriber accessresource (refer to an arrow mark 1 in FIG. 4) for a case wherein an ATMcall (fixed length cell call) from one of the ATM terminals 201 isinputted to the ATM exchange 200 by way of a corresponding one of thesubscriber lines 203 and then sent out to another one of the ATMterminals 201 by way of another one of the subscriber lines 203, framerelay terminal subscriber resource control means (second terminalsubscriber resource control means) 213 for controlling a frame relayterminal subscriber access resource (refer to another arrow mark 2 inFIG. 4) for a case wherein a frame relay call (frame call) from one ofthe frame relay terminals 202 is inputted to the ATM exchange 200 by wayof one of the subscriber lines 204 and then sent out to another one ofthe frame relay terminals 202 by way of another one of the subscriberlines 204, and network resource control means 214 for controlling anetwork common resource (refer to a further arrow mark 3 or 4 in FIG. 4)for a case wherein an ATM call from one of the ATM terminals 201 or aframe relay call from one of the frame relay terminals 202 is inputtedto the ATM exchange 200 by way of a corresponding one of the subscriberlines 203, 204 and then sent out to a trunk line 211, are provided.

The ATM terminal subscriber resource control means 212 includes ATM callacceptance determination means (fixed length cell call acceptancedetermination means) 215 for determining whether or not an ATM call fromone of the ATM terminals 201 should be accepted when the ATM terminal201 tries to use the ATM terminal subscriber access resource while theframe relay terminal subscriber resource control means 213 includesframe relay call acceptance determination means (frame call acceptancedetermination means) 216 for determining whether or not a frame relaycall from one of the frame relay terminals 202 should be accepted whenthe frame relay terminal 202 tries to use the frame relay terminalsubscriber access resource. Further, the network resource control means214 includes common resource call acceptance determination means 217 fordetermining whether or not an ATM call from one of the ATM terminals 201or a frame relay call from one of the frame relay terminals 202 shouldbe accepted when the ATM terminal 201 or the frame relay terminal 202tries to use the network common resource.

The frame relay call acceptance determination means 216 may includevirtual band calculation means for multiplying a use requested bandrequested to set from one of the frame relay terminals 202 by apredetermined multiplexing rate α to calculate a use virtual band A3which is controlled by the network, incoming side subscriber line freeband detection means for detecting a free band B3 for the incoming sidesubscriber lines 204 for the frame relay terminal, outgoing sidesubscriber line free band detection means for detecting a free band C3for the outgoing side subscriber lines 204 for the frame relay terminal,first comparison means for comparing the use virtual band A3 calculatedby the virtual band calculation means and the free band B3 detected bythe incoming side subscriber line free band detection means with eachother, second comparison means for comparing the use virtual band A3calculated by the virtual band calculation means and the free band C3detected by the outgoing side subscriber line free band detection meanswith each other, and call acceptance means for accepting a frame relaycall from one of the frame relay terminals 202 when the result ofcomparison by the first comparison means is [free band B3 for theincoming side subscriber lines 204 for the frame relay terminal]>[usevirtual band A3] and the result of comparison by the second comparisonmeans is [free band C3 for the outgoing side subscriber lines 204 forthe frame relay terminal]>[use virtual band A3].

A use requested band requested to set from one of the frame relayterminals 202 may be added as band information to a frame relay callfrom the frame relay terminal 202 and then transferred to the virtualband calculation means of the frame relay call acceptance determinationmeans 216 together with the frame relay call.

The common resource call acceptance determination means 217 may includevirtual band calculation means for multiplying a use requested bandrequested to set from one of the ATM terminals 201 or from one of theframe relay terminals 202 by a predetermined multiplexing rate β tocalculate a use virtual band A4 which is controlled by the network,common resource free band detection means for detecting a free band B4on the network common resource of the ATM exchange 200, comparison meansfor comparing the use virtual band A4 calculated by the virtual bandcalculation means and the free band B4 detected by the common resourcefree band detection means with each other, and call acceptance means foraccepting an ATM call from one of the ATM terminals 201 or a frame relaycall from one of the frame relay terminals 202 when the result ofcomparison by the comparison means is [free band B4 on the networkcommon resource]>[use virtual band A4].

In this instance, the predetermined multiplexing rate β by which a userequested band is multiplied by the virtual band calculation means mayhave two values set in advance including a first multiplexing rate β1for a use requested band requested to set from one of the ATM terminals201 and a second multiplexing rate β2 for another use requested bandrequested to set from one of the frame relay terminals 202.

Further, a use requested band requested to set from one of the framerelay terminals 202 may be added as band information to a frame relaycall from the frame relay terminal 202 and then transferred to thevirtual band calculation means of the common resource call acceptancedetermination means 217 together with the frame relay call.

By the way, the common resource call acceptance determination means 217may include, as indicated by alternate long and two short dashes linesin FIG. 4, common resource ATM call acceptance determination means(common resource fixed length cell call acceptance determination means)218 for determining whether or not an ATM call from one of the ATMterminals 201 should be accepted when the ATM terminal 201 tries to usethe network common resource, and common resource frame relay callacceptance determination means (common resource frame call acceptancedetermination means) 219 for determining whether or not a frame relaycall from one of the frame relay terminals 202 should be accepted whenthe frame relay terminal 202 tries to use the network common resource.

In this instance, the common resource frame relay call acceptancedetermination means 219 may include virtual band setting means forsetting, when setting of a frame relay call is requested from one of theframe relay terminals 202, a physical maximum speed (physical linespeed) of the frame relay, terminal 202 as a use virtual band A5 for theframe relay call, band assurance determination means for determiningwhether or not a band has been assured already for a same sendingsubscriber as the frame relay terminal 202 on the network commonresource, common resource free band detection means for detecting a freeband B5 on the network common resource of the ATM exchange 200,comparison means for comparing the use virtual band A5 set by thevirtual band setting means and the free band B5 detected by the commonresource free band detection means with each other, and call acceptancemeans described below.

The call acceptance means employed here accepts, when the band assurancedetermination means determines that a band has been assured already forthe same sending subscriber as the frame relay terminal 202, the framerelay call from the frame relay terminal 202 unconditionally, butassures, when the band assurance determination means determines that noband has been assured as yet for the same sending subscriber as theframe relay terminal 202 and the result of comparison by the comparisonmeans is [free band B5 on the network common resource]>[use virtual bandA5], the use virtual band A5, and accepts the frame relay call from theframe relay terminal 202.

The common resource frame relay call acceptance determination means 219may include virtual band setting means for setting a use requested bandrequested to set for a frame relay call from one of the frame relayterminals 202 as a use virtual band A6 for the frame relay call, bandassurance determination means for determining whether or not a band hasbeen assured already for a same sending subscriber as the frame relayterminal 202 on the network common resource, common resource free banddetection means for detecting a free band B6 on the network commonresource of the ATM exchange 200, first comparison means for comparing,when the band assurance determination means determines that no band hasbeen assured as yet for the same sending subscriber as the frame relayterminal 202, the use virtual band A6 set by the virtual band settingmeans and the free band B6 detected by the common resource free banddetection means with each other, assured band extraction means forextracting, when the band assurance determination means determines thata band has been assured for the same sending subscriber as the framerelay terminal 202, the assured band a assured already for the framerelay terminal 202, second comparison means for comparing the assuredband a extracted by the assured band extraction means and a physicalmaximum speed of the frame relay terminal 202 with each other, thirdcomparison means for comparing, when the result of comparison by thesecond comparison means is [assured band a]≦[physical maximum speed ofthe frame relay terminal 202], a sum a+A6 of the assured band a and theuse virtual band A6 requested from the frame relay terminal 202 and thephysical maximum speed of the frame relay terminal 202 with each other,remaining available band calculation means for subtracting, when theresult of comparison by the third comparison means is [suma+A6]>[physical maximum speed of the frame relay terminal 202], theassured band a from the physical maximum speed of the frame relayterminal 202 to calculate a remaining available band C6, fourthcomparison means for comparing the remaining available band C6calculated by the remaining available band calculation means and thefree band B6 detected by the common resource free band detection meanswith each other, fifth comparison means for comparing, when the resultof comparison by the third comparison means is [sum a+A6]≦[physicalmaximum speed of the frame relay terminal 202], the use virtual band A6set by the virtual band setting means and the free band B6 detected bythe common resource free band detection means with each other, and callacceptance means described below.

The call acceptance means employed here assures, when the result ofcomparison by the first comparison means or the fifth comparison meansis [free band B6 on the common resource]>[use virtual band A6], the usevirtual band A6 and accepts the frame relay call from the frame relayterminal 202, but assures, when the result of comparison by the fourthcomparison means is [free band B6 on the common resource]>[remainingavailable band C6], the remaining available band C6 and accepts theframe relay call from the frame relay terminal 202. However, when theresult of comparison by the second comparison means is [assured banda]>[physical maximum speed of the frame relay terminal 202], the callacceptance means accepts the frame relay call from the frame relayterminal 202 unconditionally.

For each of the frame relay terminals 202 connected to the ATM exchange200 by way of the respective subscriber lines 204, a use band table maybe provided for controlling and storing a physical maximum speed(physical line speed) of the frame relay terminal 202 and a sum total ofuse requested bands which have been requested to set before the presentpoint of time by the frame relay terminal 202, and the assured bandextraction means may extract the sum total of the use requested bands ofthe use band table as the band a assured already for the frame relayterminal 202 whereas the physical maximum speed of the frame relayterminal 202 which is to be used by the second comparison means, thethird comparison means and the remaining available band calculationmeans is read out from the use band table.

Further, a use requested band (A6) requested to set from one of theframe relay terminals 202 may be added as band information to a framerelay call from the frame relay terminal 202 and then transferred to thevirtual band setting means of the common resource frame relay callacceptance determination means 219 together with the frame relay call.

In the system described above, the ATM terminal resource and the framerelay terminal resource are set such that they commonly share theresource of the ATM exchange 200, and the ATM terminal subscriber accessresource indicated by the arrow mark 1 in FIG. 4 and the frame relayterminal subscriber access resource indicated by the arrow mark 2 inFIG. 4 are controlled by the ATM terminal subscriber resource controlmeans 212 and the frame relay terminal subscriber resource control means213, respectively, while the network common resource indicated by thearrow mark 3 or 4 in FIG. 4 is controlled by the network resourcecontrol means 214.

Then, when an ATM terminal 201 tries to use the ATM terminal subscriberaccess resource, the ATM call acceptance determination means 215determines whether or not the ATM call from the ATM terminal 201 shouldbe accepted, but when a frame relay terminal 202 tries to use the framerelay terminal subscriber access resource, the frame relay callacceptance determination means 216 determines whether or not the framerelay call from the frame relay terminal 202 should be accepted.Further, when an ATM terminal 201 or a frame relay terminal 202 tries touse the network common resource, the common resource call acceptancedetermination means 217 determines whether or not the ATM call from theATM terminal 201 or the frame relay call from the frame relay terminal202 should be accepted.

Also where the resource of the ATM exchange 200 is shared commonly bythe ATM terminals and the frame relay terminals, control of the ATMterminal subscriber access resource and call acceptance determinationand control of the frame relay terminal subscriber access resource andcall acceptance determination are performed individually, but control ofthe network common resource and call acceptance determination areprocessed in accordance with an algorithm common to an ATM call from anATM terminal 201 and a frame relay call of a frame relay terminal 202.Consequently, the ATM terminals 201 and the frame relay terminals 202can be accommodated into the same ATM exchange 200.

In this instance, the frame relay call acceptance determination means216 multiplies a use requested band requested to set from one of theframe relay terminals 202 by a predetermined multiplexing rate α tocalculate a use virtual band A3 which is controlled by the network,supervises a free band B3 for the incoming side subscriber lines 204 forthe frame relay terminal and a free band C3 for the outgoing sidesubscriber lines 204 for the frame relay terminal, and accepts the framerelay call from the frame relay terminal 202 in the case of [free bandB3]>[use virtual band A3] and [free band C3]>[use virtual band A3].

Meanwhile, the common resource call acceptance determination means 217multiplies a use requested band requested to set from one of the ATMterminals 201 or from one of the frame relay terminals 202 by apredetermined multiplexing rate β (or β1 or β2) to calculate a usevirtual band A4 which is controlled by the network, supervises a freeband B4 on the network common resource of the ATM exchange 200, andaccepts the ATM call from the ATM terminal 201 or the frame relay callfrom the frame relay terminal 202 in the case of [free band B4]>[usevirtual band A4].

The common resource call acceptance determination means 217 may includethe common resource ATM call acceptance determination means 218 and thecommon resource frame relay call acceptance determination means 219 sothat call acceptance determination processing may be performed inaccordance with separate algorithms for an ATM call from one of the ATMterminals 201 and a frame relay call from one of the frame relayterminals 202 on the network common resource.

In this instance, the common resource frame relay call acceptancedetermination means 219 sets, when setting of a frame relay call isrequested from one of the frame relay terminals 202, a physical maximumspeed (physical line speed) of the frame relay terminal 202 as a usevirtual band A5 for the frame relay call, supervises a free band B5 onthe network common resource of the ATM exchange 200, and accepts, when aband has been assured already for the same sending subscriber as theframe relay terminal 202, the frame relay call from the frame relayterminal 202 unconditionally, but assures, when no band has been assuredas yet for the same sending subscriber as the frame relay terminal 202and the free band B5 is greater than the use virtual band A5, the usevirtual band A5 and accepts the frame relay call from the frame relayterminal 202.

Meanwhile, the common resource frame relay call acceptance determinationmeans 219 sets a use requested band requested to set for a frame relaycall from one of the frame relay terminals 202 as a use virtual band A6for the frame relay call, supervises a free band B6 on the networkcommon resource of the ATM exchange 200, and compares, when no band hasbeen assured as yet for the same sending subscriber as the frame relayterminal 202, the use virtual band A6 set by the virtual band settingmeans and the free band B6 detected by the common resource free banddetection means with each other, but extracts, when a band has beenassured for the same sending subscriber as the frame relay terminal 202,the assured band a assured already for the frame relay terminal 202 andsubtracts, in the case of [assured band a]≦[physical maximum speed ofthe frame relay terminal 202] and [sum a+A6]>[physical maximum speed ofthe frame relay terminal 202], the assured band a from the physicalmaximum speed of the frame relay terminal 202 to calculate a remainingavailable band C6 and then compares, in the case of [sum a+A6]≦[physicalmaximum speed of the frame relay terminal 202], the use virtual band A6and the free band B6 detected by the common resource empty banddetection means with each other.

Then, the common resource frame relay call acceptance determinationmeans 219 may assure, when the result of comparison between the usevirtual band A6 and the free band B6 described above is [free bandB6]>[use virtual band A6], the use virtual band A6 and accept the framerelay call from the frame relay terminal 202, but assure, in the case of[free band B6]>[remaining available band C6], the remaining availableband C6 and accept the frame relay call from the frame relay terminal202, but accept, in the case of [assured band a]>[physical maximum speedof the frame relay terminal 202], the frame relay call from the framerelay terminal 202 unconditionally.

Further, where a use band table is provided for each of the frame relayterminals 202 for controlling and storing a physical maximum speed(physical line speed) of the frame relay terminal 202 and a sum total ofuse requested bands which have been requested to set before the presentpoint of time by the frame relay terminal 202, the sum total of userequested bands of the use band table can be used for the assured band afor the frame relay terminal 202, and besides, the physical maximumspeed of the frame relay terminal 202 which is required for variouscomparison processing and for calculation processing of the remainingavailable band C6 can be read out from the use band table and used forsuch processing.

Further, where a use requested band requested to set from one of theframe relay terminals 202 is transferred as band information to theframe relay call acceptance determination means 216 or the commonresource frame relay call acceptance determination means 219 togetherwith the frame relay call, the user of the frame relay terminal 202 neednot any more report a use requested band every time before a call isdeveloped.

With the frame relay exchanging method by an ATM exchange and the framerelay exchanging interface apparatus of the present inventionconstructed in such a manner as described above, the following effectsand/or advantages can be achieved.

1. A frame relay packet having a variable data length can be exchangedat a high speed by the ATM exchange.

2. Since a predetermined corresponding relationship is provided betweena used channel number upon communication of a frame relay packet anddata link connection identifier information and ATM communicationchannel identifier information of a destination of transmission, a hardlogic routing function can be provided, and when it is tried toaccommodate a frame relay terminal into the ATM exchange, assemblyand/or disassembly of a cell or routing on hardware for a frame relaypacket can be realized readily.

3. Since a cell relay between different ATM exchanges is the same as inordinary ATM exchange, there is no need of particularly getting aware ofa frame relay, and a frame relay terminal can be accommodated into anATM exchange using an existing ATM technique as it is. Further, aservice of accommodating and connecting a frame relay terminal into andto an ATM exchange can be realized as one of services of the ATMexchange.

Further, width the call acceptance determination system for an ATMexchange of the present invention, the following effects and/oradvantages can be achieved.

4. By dividing the resource of an ATM exchange simply, control of theATM terminal resource and call acceptance determination can be processedcompletely independently of control of the frame relay terminal resourceand call acceptance determination, and an ATM terminal and a frame relayterminal can be accommodated very readily into the same ATM exchange anda service of accommodating and connecting a frame relay terminal intoand to the ATM exchange can be realized as one of services of the ATMexchange.

5. Since control of the ATM terminal subscriber access resource and callacceptance determination and control of the frame relay terminalsubscriber access resource and call acceptance determination areperformed by the ATM call acceptance determination means and the framerelay call acceptance determination means, respectively, and control ofthe network common resource and call acceptance determination areperformed by the common resource call acceptance determination means,even where the resource of the ATM exchange is shared commonly for theATM terminals and the frame relay terminals, an ATM terminal and a framerelay terminal can be accommodated very readily into the same ATMexchange, and a service of accommodating and connecting a frame relayterminal into and to the ATM exchange can be realized as one of servicesof the ATM exchange.

6. Since a use requested band is added as band information to an ATMcall or a frame relay call, a user of a frame relay terminal need notany more report a use requested band every time before a call isdeveloped, and further enhancement in service can be achieved.

7. Since at least one path from a certain frame relay terminal is set onthe lines, a band for a physical maximum speed is assured whereas a bandhigher than the physical maximum speed is not assured, and consequently,a contract for a speed higher than the physical maximum speed can beallowed for each of the frame relay terminals. Then, when a frame relayterminal is accommodated into the ATM exchange so as to offer a framerelay service, a path for the frame relay can be set to the ATM switchednetwork in the same conditions as the existing frame relay services andbesides effective utilization of the resource can be realized.

8. Since call acceptance determination processing is performed using thefirst and second multiplexing rates conforming to characteristics of anATM call and a frame relay call and the common resource call acceptancedetermination means is divided into the common resource ATM callacceptance determination means and the common resource frame relay callacceptance determination means, call acceptance determination processingcan be performed in accordance with separate algorithms for an ATM callfrom an ATM terminal and a frame relay call from a frame relay terminalon the network common resource, and by assuring a band for paths for allof the frame relay terminals as a virtual band, effective utilization ofthe common resource can be realized.

9. By performing call acceptance determination processing such that,when the sum total of use requested bands requested to set from a framerelay terminal before the present point of time is lower than thephysical maximum speed, a band is assured with the sum total of userequested bands, but when the sum total of use requested bands exceedsthe physical maximum speed, a band is assured with the physical maximumspeed, the common resource of the ATM exchange can be utilized furthereffectively.

10. Since the physical maximum speed and the sum total of use requestedbands requested to set before the present point of time are controlledand stored by means of the use band table, the sum total of userequested bands of the use band table can be used as an assured band ofthe frame relay terminal, and besides, the physical maximum speed of theframe relay terminal which is required for various comparison processingor for calculation processing of a remaining available band can be readout from the use band table and used for such processing. Consequently,control of various data and calculation processing of various means canbe performed efficiently.

b. First Embodiment

Referring to FIG. 5, there is shown a frame relay exchanging interfaceapparatus (variable length frame exchanging interface apparatus)according to a first preferred embodiment of the present invention. Thevariable length frame exchanging interface apparatus (hereinafterreferred to as interface unit) 151 is interposed between a frame relayterminal 100 and an ATM exchange 150 which are interconnected by way ofsubscriber lines (a DS1 line 152 as a digital transmission line and anoptical cable 153) having at least one channel. The frame relay terminal100 is used for a data communication method by a variable length frame(hereinafter referred to as frame relay packet) including logic channelinformation while the ATM exchange 150 handles fixed length cells(hereinafter referred to as ATM cells) each including a logic channelinformation section and a data section. The interface unit 151 is thusconnected to the frame relay terminal 100 by way of the DS1 line (forexample, PCM 24 lines) 152 as a subscriber line and also to the ATMexchange 150 by way of the optical cable 153 as another subscriber line.

The interface unit 151 performs conversion processing between ATM cellsfor the ATM exchange 150 and a frame relay packet for the frame relayterminal 100 and includes, to this end, a DS1 interface section (lineterminating section) 154, a frame processing section 155 and an opticalinterface section (ATM exchange interface section) 156.

The DS1 interface section 154 may be constructed in such a manner ashereinafter described with reference to FIG. 6 and terminates a signalof the DS1 line 152 between the subscriber (frame relay terminal 100)and the interface unit 151. The frame processing section 155 may beconstructed in such a manner as hereinafter described with reference toFIG. 7 and extracts, on one hand, a frame from a signal on the DS1 line152 terminated at the DS1 interface section 154 and converts the frameinto ATM cells. On the other hand, the frame processing section 155extracts a frame from ATM cells and delivers the frame to the DS1interface section 154. The optical interface section 156 may beconstructed in such a manner as hereinafter described with reference toFIG. 8 and terminates a signal of the optical cable 153 between the ATMexchange 150 and the interface unit 151.

The construction of the DS1 interface section 154 will be described indetail below with reference to FIG. 6. The DS1 interface section 154includes a bipolar to unipolar (bipolar/unipolar) conversion section 157for converting an electric signal (bipolar signal; a transmission signalfrom the frame relay terminal 100) on the DS1 line 152 received from theframe relay terminal 100 by way of the DS1 line 152 into anintra-circuit signal (unipolar signal) and extracting a DS1 receptionclock signal (of, for example, 1.544 MHz) from the electric signal, anda unipolar to bipolar (unipolar/bipolar) conversion section 158 forconverting an intra-circuit signal (unipolar signal) into an electricsignal (bipolar signal; a call-in signal to the frame relay terminal100) on the DS1 line 152 in response to a DS1 transmission clock signal(of, for example, 1.544 MHz) from a DS1 transmission control section 160which will be hereinafter described.

The DS1 interface section 154 further includes a DS1 reception controlsection 159 in the form of a transmission receiving processor LSI (TRPLSI) for terminating a reception signal (DS1 reception data,corresponding to a transmission frame relay packet from the frame relayterminal 100) from the bipolar to unipolar conversion section 157 toextract payload data and extracting a control signal (Extended SuperFrame DATA Link: ESF data link) on the DS1 line 152.

The DS1 interface section 154 further includes a DS1 transmissioncontrol section 160 in the form of a transmission sending processor LSI(TSP LSI) for converting payload data (transmission data) and an ESFdata link into a transmission signal of the DS1 format (corresponding toa call-in frame relay packet to the frame relay terminal 100) andcontrolling transmission of the transmission signal to the frame relayterminal 100 by way of the unipolar to bipolar conversion section 158.

The DS1 interface section 154 further includes a data link controlsection 161 in the form of an embedded operation channel LSI (EOC LSI)which has a function of extracting a maintenance control informationchannel (EOC) from an ESF data link, another function of terminating theESF data link, and a further function of processing various maintenancecontrol information on the maintenance control information channel.

The DS1 interface section 154 further includes a microprocessor 162 forperforming detection of a trouble, measurement of a performance and soforth, a ROM 163 in which programs and data necessary to operate themicroprocessor 162 are stored, and a RAM 164 for storing variable datato be used by the microprocessor 162.

The DS1 interface section 154 further includes a processor-to-processorcommunication register 165 for performing communication with amicroprocessor 175 of the frame processing section 155, a power source166 (On Board Power: OPB) for supplying the power of, for example, +5 Vto the circuit components, a phase locked loop (PLL) circuit 167 forproducing a CPU clock signal of, for example, 12.352 MHz from a basicclock signal of, for example, 8 kHz, and a timing generator (TMG) 168for producing a controlling clock signal of, for example, 3.088 MHz fromthe clock signal of 12.352 MHz from the PLL circuit 167.

The construction of the frame processing section 155 is shown in moredetail in FIG. 7. Referring to FIG. 7, the frame processing section 155includes a transmission data conversion section 169 in the form of a BICLSI for converting data of, for example, 3.088 MHz into data of, forexample, 1.544 MHz in the transmission direction of the frame processingsection 155, that is, in the direction in which a call-in frame relaypacket is transmitted to the frame relay terminal 100, and a timingproduction section 170 for generating a timing signal (Upward Timing:UTG) necessary for a media conversion section 171 and a data controlsection 172, which will be hereinafter described, from a clock signal of1.544 MHz synchronized with a PCM link and for generating another timing(Downward Timing: DTG) signal necessary for the media conversion section171 and the data control section 172 from a clock signal of 3.088 MHzsynchronized with the optical interface.

The media conversion section 171 in the form of MACH 138 LSI functionsas frame relay packet production means (refer to reference numeral 111in FIG. 1 and 131 in FIG. 2) and call-in frame relay packetdisassembling means (refer to reference numeral 124 in FIG. 1 and 138 inFIG. 2) in the present invention.

In particular, the media conversion section 171 has a function as framerelay packet production means 171A (refer to FIG. 9) of extracting andproducing a transmission frame relay packet (frame of the LAP-F) fromdata (reception data at the interface unit 151) for 24 channels from theDS1 interface section 154 in response to channel number controlinformation obtained by the data control section 172 which will behereinafter described, and another function as call-in frame relaypacket disassembling means 171B (refer to FIG. 10) of disassembling data(transmission data to the interface unit 151) from a cellassembling/disassembling section 178, which will be hereinafterdescribed, into a call-in frame relay packet in response to channelnumber control information obtained by the data control section 172,which will be hereinafter described, and inserting the reception framerelay packet into a particular channel.

The data control section 172 in the form of an SSMC LSI functions aschannel number to virtual path identifier information conversion means(refer to reference numeral 112 in FIG. 1 and 132 in FIG. 2), data linkconnection identifier information to virtual channel identifierinformation conversion means (refer to reference numeral 113 in FIG. 1and 133 in FIG. 2), virtual path identifier information to channelnumber conversion means (refer to reference numeral 123 in FIG. 1 and137 in FIG. 2) and virtual channel identifier information conversionmeans to data link connection identifier information conversion means(refer to reference numeral 122 in FIG. 1 and 136 in FIG. 2) in thepresent invention.

The data control section 172 controls allocation information of achannel number or numbers, a DLCI number and VPI (virtual pathidentifier information)/VCI (virtual channel identifier information) andaccesses an SRAM 173, which will be hereinafter described, to obtainvarious information (a channel number or numbers, a DLCI number, a VPIand a VCI) which is to be added to data.

Accordingly, the data control section 172 has a function as channelnumber to VPI conversion means of accessing the SRAM 173 to convert achannel number or numbers (1 to 24) of the DS1 line 152, which have beenused upon transmission of a transmission frame relay packet from theframe relay terminal 100) into a VPI, another function as DLCI to VCIconversion means of accessing the SRAM 173 to convert a DLCI added tothe transmission frame relay packet into a VCI, a further function asVCI to DLCI conversion means of accessing the SRAM 173 to convert a VCIadded to each ATM cell from the optical interface section 156 into aDLCI, and a still further function of the VPI to channel numberconversion means of accessing the SRAM 173 to convert a VPI added toeach ATM cell from the optical interface section 156 into a channelnumber or numbers of the DS1 line 152 available upon transmission to theframe relay terminal 100.

A VPI and a VCI obtained by conversion of a channel number of numbersand a DLCI, respectively, by the data control section 172 are added asrouting information (ATM communication channel identifier information)to each ATM cell by the cell assembling/disassembling section 178 whichwill be hereinafter described. Meanwhile, a DLCI obtained by conversionof the VCI by the data control section 172 is added to a call-in framerelay packet to the frame relay terminal 100. Further, a channel numberof numbers obtained by conversion of the VPI by the data control section172 are used as information of a particular channel or channels intowhich the call-in frame relay packet after disassembled is to beinserted by the media conversion section 171 (call-in frame relay packetdisassembling means 171B).

The SRAM 173 functions as first storage means (refer to referencenumerals 115 and 125 in FIG. 1 and reference numeral 139 in FIG. 2) andsecond storage means (refer to reference numerals 116 and 126 andreference numeral 140 in FIG. 2) in the present invention. The SRAM 173stores such channel number control information and mutual relationships(tables) among VPI information. VCI information, DLCI information andchannel numbers as will be hereinafter described with reference to FIGS.11 to 13.

In particular, the SRAM 173 stores in advance a first relationshipbetween VPI information and channel numbers of the DS1 line 152 which isaccessed from the channel number to VPI conversion means and the VPI tochannel number conversion means of the data control section 172 and usedbetween the frame relay terminal 100 and the ATM exchange 150, and asecond relationship between VCI information and DLCI information whichis accessed from the DLCI to VCI conversion means and the VCI to DLCIconversion means of the data control section 172 and is to be added to aframe relay packet.

The first and second relationships (mapping relationships) stored in theSRAM 173 may be such tables (conversion tables) as illustrated in FIGS.11 or 12 and 13.

Referring first to FIG. 11, in the table shown, a relationship betweenthe channel number and the DLCI number is allocated in a fixed logicalrelationship to the VPI number and the VCI number. In particular, when achannel number/DLCI is to be converted into a VPI/VCI, such a fixedlogic is applied that, when a frame relay packet is to be communicatedwith the frame relay terminal 100, the lowest one (lowest channelnumber: LCH) of the channel numbers (1 to 24) of the DS1 line 152 isused as a VPI number while a DLCI number is used as it is as a VCInumber. On the contrary when a VPI/VCI is to be converted into a channelnumber/DLCI, such a fixed logic is applied that a channel number groupin which the VPI is included as the lowest number is read out as achannel number (1 to 24) group of the DS1 line 152 while a VCI number isused as it is as a DLCI number.

More particularly, as seen from FIG. 11, for a frame relay packettransmitted from the frame relay terminal 100 using one of the channelnumbers 1, 5, 10 and 13 of the DS1 line 152, the lowest number 1 amongthe channel numbers is used as a VPI after disassembly into ATM cells.On the other hand, for a frame relay packet transmitted using one of thechannel numbers 3, 7 and 12, the lowest number 3 among the channelnumbers is used as a VPI. Further, the DLCI number 1, 4, 5 or 9, or 4 or10 applied to the frame relay packet and designating the other party isused as it is as a VCI.

On the contrary, for ATM cells received from the ATM exchange 150 anddesignating the frame relay terminal 100 as a destination oftransmission, if the VPI number is 1 or 3, then the group of channelnumbers 1, 5, 10 and 13 or 3, 7 and 12 in which the VPI number isincluded as the lowest number is read out from the table shown in FIG.11, and the channel number group is used as information of a particularchannel which is to be inserted into a reception frame relay packetafter disassembly by the media conversion section 171 (call-in framerelay packet disassembling means 171B) as described hereinabove.Meanwhile, the VCI number 1, 4, 5 or 9, or 4 or 10 applied to the ATMcell is used as it is as a DLCI.

Meanwhile, in the tables shown in FIGS. 12 and 13, such a fixed logic asdescribed hereinabove with reference to FIG. 11 is not used, but a table(conversion table) which depends upon an arbitrary correspondingrelationship is set suitably in advance. In particular, as seen fromFIG. 12, the lowermost number of a channel number group of the DS1 line152 which is used upon communication of a frame relay packet with theframe relay terminal 100 corresponds in a one-by-one correspondingrelationship to a VPI number of ATM cells, and as seen in FIG. 13, aDLCI number to be applied to a frame relay packet and a VCI number ofATM cells correspond in a one-by-one corresponding relationship to eachother.

Such a table as shown in FIG. 11 or such tables as shown in FIGS. 12 and13 are stored in advance in the SRAM 173, and in response to an accessfrom the data control section 172 described hereinabove, such acorresponding relationship as described hereinabove is read out, andconversion between a channel number group and a VPI number andconversion between a DLCI and a VCI are performed. Such a correspondingrelationship (mapping relationship) in the first embodiment as describedabove is conceptively illustrated in FIG. 14. As seen from FIG. 14, aDLCI (logic link of the LAP-F) of a frame relay and a VCI in ATMexchange are mapped in a one-by-one corresponding relationship, and achannel number group on the DS1 (PCM24) line 152 used as a frame relaycorresponds to a VPI in ATM exchange and the lowest number in thechannel number group is mapped in a one-by-one correspondingrelationship to a VPI.

Referring to FIGS. 9 and 10, a storage section 173A in the SRAM 173stores a channel number group on the DS1 line 152, that is, acombination pattern of channels in advance and provides channel numbercontrol information to the media conversion section 171 in response toan access thereto from the data control section 172. Meanwhile, anotherstorage section 173B in the SRAM 173 stores in advance the first andsecond corresponding relationships (such a one-by-one correspondingrelationship between a lowest channel number and a VPI number asillustrated in FIG. 17 and another one-by-one corresponding relationshipbetween a DLCI number and a VCI number) based on, for example, such afixed logic as described hereinabove with reference to FIG. 11, andprovides such corresponding relationship information to the cellassembling/disassembling section 178 in response to an access theretofrom the data control section 172. It is to be noted the data controlsection 172 is omitted in FIGS. 9 and 10.

Referring back to FIG. 7, the frame processing section 155 furtherincludes a working SRAM 174, a microprocessor 175 for controlling(detection of a trouble, processing control and so forth) of thecomponent LSIs (refer to reference numerals 169, 171 and 172), a ROM 176in which programs and data necessary to operate the microprocessor 175are stored, and an LSI control section (SOS LSI) 177 for controlling thecomponent LSIs (refer to reference numerals 169, 171 and 172) togetherwith the microprocessor 175.

The frame processing section 155 further includes the cellassembling/disassembling section (cell assembly re-assembly processorLSI: CARP LSI) 178 which functions as transmission frame relay packetdisassembling means (refer to reference numeral 114 in FIG. 1 and 134 inFIG. 2) and frame relay packet composition means (refer to referencenumeral 121 in FIG. 1 and 135 in FIG. 2) in the present invention.

In particular, the cell assembling/disassembling section 178 has atransmission processing function of converting a signal (transmissionframe relay packet) from the DS1 interface section 154 stored in a RAM179, which will be hereinafter described, into ATM cells andtransferring the ATM cells to the optical interface section 156, thatis, a function as transmission frame relay packet disassembling means178A (refer to FIG. 9) of disassembling a transmission frame relaypacket into ATM cells to which a VPI and a VCI obtained by the datacontrol section 172 are added and sending out the ATM cells to the ATMexchange 150, and another reception processing function of fetchingcall-in data (ATM cells) from the ATM exchange 150 stored in the RAM 179by a DMA (Direct Memory Accessing) operation and transferring the dataafter production of a format to the DS1 interface section 154 by way ofthe media conversion section 171, that is, a function as frame relaypacket assembling means 178B (refer to FIG. 10) of assembling a call-inframe relay packet in response to ATM cells from the ATM exchange 150designating the frame relay terminal 100 as a destination oftransmission.

The frame processing section 155 further includes the RAM 179 controlledby the cell assembling/disassembling section 178 for temporarily storingcells upon processing by the cell assembling/disassembling section 178and converting the speed between the DS1 line 152 and the cells, a pairof microprocessor interface sections (MP-INF) 180 and 181 forcommunicating control information between the microprocessor 162 of theDS1 interface section 154 and another microprocessor (not shown) of theoptical interface section 156, and a parity checking section 182 forchecking the parity of data of the SRAM 173 or the working SRAM 174.

A detailed construction of the optical interface section 156 is shown inFIG. 8. Referring to FIG. 8, the optical interface section 156 includesa transmission cell speed conversion section 183 in the form of a FIFO(first-in first-out) memory for controlling the conversion of the speedof ATM cells from the frame processing section 155, a call-in cell speedconversion section 184 also in the form of a FIFO memory for controllingthe conversion of the speed of ATM cells to the frame processing section155, and a speed conversion control section 185 for generating a timingsignal in accordance with which communication and cell control by thetransmission cell speed conversion section 183 and the call-in cellspeed conversion section 184 are to be performed.

The optical interface section 158 further includes a cell data parallelto serial (parallel/serial) conversion section 186 for convertingascending cell data (a parallel signal) from the transmission cell speedconversion section 183 into a serial signal with a basic clock signal(for example, of 8 MHz) of an interface section 190 which will behereinafter described, and a cell data serial to parallel(serial/parallel) conversion section 187 for converting descending celldata (a serial signal) from the interface section 190 into a parallelsignal.

The optical interface section 156 further includes a cell dataassembling section 188 for converting a cell signal from the cell dataparallel to serial conversion section 186 into a signal of a format ofthe interface section 190, a cell data control section 189 forcontrolling a synchronizing clock signal of a cell signal of theinterface section 190, and the interface section 190 for converting anelectric signal from the cell data assembling section 188 into anoptical signal and sending out the optical signal to the optical cable153 and for converting an optical signal transmitted thereto from theATM exchange 150 by way of the optical cable 153 into an electric signaland sending out the electric signal to the cell data serial to parallelconversion section 187.

Subsequently, operation of the interface unit 151 of the firstembodiment having such construction as described above, that is, a framerelay conversion method by the ATM exchange according to the presentinvention, will be described.

First, transmission of a frame relay packet from the frame relayterminal 100 to the ATM exchange 150 will be described.

A transmission frame relay packet transmitted from the frame relayterminal 100 by way of the DS1 line 152 is terminated by the DS1interface section 154 of the interface unit 151. In particular, anelectric signal (bipolar signal) on the DS1 line 152 transmitted fromthe frame relay terminal 100 is converted into an intra-circuit signal(unipolar signal) by the bipolar to unipolar conversion section 157 andis then terminated by the DS1 reception control section 159 to extractpayload data, which are sent to the frame processing section 155.

In the frame processing section 155, from the data for 24 channels fromthe DS1 interface section 154, a transmission frame relay packet (aframe of the LAP-F) is extracted and generated by the media conversionsection 171 (frame relay packet production means 171A in FIG. 9) inresponse to channel number control information obtained by the datacontrol section 172.

In particular, a transmission frame relay packet of the LAP-F isproduced by the frame relay packet production means 171A from the datatransmitted from the frame relay terminal 100 by way of a plurality ofchannels of the DS1 line 152 in accordance with a combination table(refer to, for example, FIG. 16) of channel number groups registered inthe storage section 173A of the SRAM 173 in advance.

In this instance, the data control section 172 extracts the lowestchannel number (LCH) from the combination in the channel number groupand uses the lowest channel number as a VPI for conversion into ATMcells in accordance with the corresponding relationship (refer to, forexample, FIG. 17) registered in the storage section 173B of the SRAM 173in advance (a function of conversion from a channel number or numbersinto a VPI).

Meanwhile, the format of the transmission frame relay packet produced bythe frame relay packet production means 171A is such as illustrated inFIG. 15 wherein a flag (01111110) is provided at the top and the end ofthe transmission frame relay packet and a DLCI for identification of adestination of transmission is set subsequently to the flag at the top,and variable length information is disposed subsequently to the DLCI.The data control section 172 obtains such DLCI information from thetransmission frame relay packet of the format described above, reads outa VCI corresponding to the DLCI information from the table registered inadvance in the SRAM 173 and applies the VCI upon conversion into an ATMcell (a function of conversion from a DLCI to a VCI).

The transmission frame relay packet produced by the frame relay packetproduction means 171A of the media conversion section 171 is stored onceinto the RAM 179, then disassembled, by the cellassembling/disassembling section 178 (transmission frame relay packetdisassembling means 178A of FIG. 9), into ATM cells to each of which theVPI and the VCI from the data control section 172 have been applied, andthen transferred to the optical interface section 156.

In this instance, in the transmission frame relay packet disassemblingmeans 178A, using a buffer memory or the like, the variable lengthinformation in the transmission frame relay packet is disassembled by 48octets of a fixed length (corresponding to the length of the informationsection of the ATM cell) as illustrated in FIG. 15, and simultaneously,the VPI and the VCI from the data control section 172 which make routinginformation for the ATM exchange 150 are placed into the header of 5octets of each ATM cell. The transmission frame relay packet isdecomposed into a plurality of ATM cells having information of 48 octetsas seen in FIG. 15 in this manner, and a header of 5 octets in which thesame VPI and VCI are disposed is added to the top of each ATM cell. SuchATM cells are successively sent out to the optical interface section156.

In the optical interface section 156, each ATM cell from the frameprocessing section 155 is controlled by speed conversion control by thetransmission cell speed conversion section 183 which operates inresponse to a timing signal from the speed conversion control section185, and then converted into a serial signal with a basic clock signalof the interface section 190 by the cell data parallel to serialconversion section 186.

The cell data after conversion into a serial signal are converted intodata of the format of the interface section 190 by the cell dataassembling section 188 and then converted into an optical signal by theinterface section 190, and the optical signal is sent out to the ATMexchange 150 by way of the optical cable 153.

Consequently, the frame relay packet from the frame relay terminal 100is exchanged as ATM cells by the ATM exchange 150 in accordance with theVPI and the VCI as routing information.

On the other hand, when ATM cells designating the frame relay terminal100 as a destination of transmission is received from the ATM exchange150 by way of the optical cable 153, each of the ATM cells is terminatedby the optical interface section 156 of the interface unit 151. Inparticular, each ATM cell is converted from an optical signal into anelectric signal by the interface section 190, converted into a parallelsignal by the cell data serial to parallel conversion section 187,controlled by speed conversion control by the call-in cell speedconversion section 184 which operates in response to a timing signalfrom the speed conversion control section 185, and then sent to theframe processing section 155.

In the frame processing section 155, call-in data (ATM cells) from theoptical interface section 156 are stored once into the RAM 179 and thenfetched by a DMA operation by the cell assembling/disassembling section178 (call-in frame relay packet assembling means 178B of FIG. 9), inwhich they are assembled into a call-in frame relay packet. The call-inframe relay packet is transferred to the media conversion section 171.

In this instance, the data control section 172 refers to the storagesection 173B of the SRAM 173 in response to the VPI and the VCI appliedto each of the ATM cells to read out the lowest channel number (refer toFIG. 17) corresponding to the VPI (a function of conversion from a VPIinto a channel number or numbers) and also read out a DLCI numbercorresponding to the VCI (another function of conversion from a VCI intoa DLCI).

Subsequently, the media conversion section 171 reads out a channelnumber group (channel control information) corresponding to the lowestchannel number obtained by conversion of the VPI from the storagesection 173A of the SRAM 173, and then, the media conversion section 171(call-in frame relay packet disassembling means 171B of FIG. 9) adds theDLCI from the data control section 172 to the reception frame relaypacket to the frame relay terminal 100, disassembles and inserts thereception frame relay packet into the channel number group from the datacontrol section 172 and sends the resulted data to the DS1 interfacesection 154.

The DS1 interface section 154 converts the payload data (transmissiondata) and the ESF data link from the frame processing section 155 intodata of the DS1 format by the DS1 transmission control section 160, andthe unipolar to bipolar conversion section 158 converts theintra-circuit signal (unipolar signal) into an electric signal (bipolarsignal) for the DS1 line 152 in response to a DS1 transmission clocksignal (for example, 1.544 MHz) from the DS1 transmission controlsection 160 and transmits the electric signal to the frame relayterminal 100.

In this manner, according to the first embodiment, a frame relay packethaving a variable data length can be exchanged at a high speed by theATM exchange 150.

Further, where a fixed logical or arbitrary corresponding relationship(mapping relationship) is provided between a used channel number ornumbers and a DLCI number of a destination of transmission uponcommunication of a frame relay packet and a VPI and a VCI which arerouting information in ATM exchange, a hard logic routing function canbe provided.

Accordingly, when the frame relay terminal 100 is to be accommodatedinto the ATM exchange 150, assembling/disassembling of cells or routingby hardware can be realized readily for a frame relay packet.

Further, where such a fixed logic as described hereinabove is employed,allocation processing between a channel number or numbers and DLCI andATM communication channel identifier information (routing information)is simplified and the cost for hardware can be reduced.

Further, since a cell relay between the ATM exchange 150 and another ATMexchange is the same as in ordinary ATM exchange, there is no need ofparticularly getting aware of a frame relay, and the frame relayterminal 100 can be accommodated into the ATM exchange 150 using theexisting ATM technique as it is and a service of accommodating andconnecting the frame relay terminal 100 into and to the ATM exchange 150can be realized as one of services of the ATM exchange.

It is to be noted that, while the interface unit 151 in the firstembodiment is described such that it has a transmission processingfunction (refer to FIG. 9) of disassembling a frame relay packet fromthe frame relay terminal 100 into ATM cells and transmitting the ATMcells to the ATM exchange 150 and another call-in processing function(refer to FIG. 10) of assembling ATM cells from the ATM exchange 150into a frame relay packet and sending the frame relay packet to theframe relay terminal 100, two separate frame relay exchanging interfaceapparatus having only different ones of the two functions from eachother may be constructed alternatively. Also in this instance, similareffects to those of the embodiment described above can be achieved. Inthis instance, however, on the transmission side of a frame relaypacket, an interface apparatus having such a construction as shown inFIG. 9 (or the apparatus 110 shown in FIG. 1) is provided, and on thecall-in side of the frame relay packet, another interface apparatushaving such a construction as shown in FIG. 10 (or the apparatus 120shown in FIG. 1) is provided.

c. Second Embodiment

Referring now to FIG. 18, there is shown an ATM exchange system as asecond preferred embodiment of the present invention. The ATM exchangesystem shown is generally denoted at 220 and includes an ATM exchange200 which handles fixed length cells each including a logic channelinformation section and a data section and accommodates a plurality ofATM terminals 201 as first terminals for use with a data communicationmethod by fixed length cells (hereinafter referred to as ATM cells) byway of respective ATM terminal subscriber lines 203 and furtheraccommodates a plurality of frame relay terminals 202 as secondterminals for use with another data communication method by a variablelength frame (hereinafter referred to as frame relay packet) includinglogic channel information by way of respective frame relay terminalsubscriber lines 204.

The resource (free band) of the ATM exchange 200 is set dividedphysically completely separately into an ATM terminal switch resource221 and a frame relay terminal switch resource 222. Accordingly, alsotrunk circuits of the ATM exchange 200 are completely separated into ATMterminal trunk lines 205 and frame relay terminal trunk lines 206.

It is to be noted that such an interface unit 151 as describedhereinabove in connection with the first embodiment is interposed ineach of the frame relay terminal subscriber lines 204 and the framerelay terminal trunk lines 206 so that, by way of such interface unit151, a frame relay packet from the corresponding frame relay terminal202 is converted into ATM cells and inputted to the ATM exchange 200 orATM cells from the ATM exchange 200 are converted into a frame relaypacket and sent out to the frame relay terminal 202.

The ATM exchange system 220 further includes a call processor 223 forcontrolling processing of a call by the ATM exchange 200. The callprocessor 223 includes a service control section 224 serving as callprocessing software for performing band control, an ATM terminalresource control section 225 and a frame relay terminal resource controlsection 226.

The service control section 224 performs a service analysis, numericinterpretation and path control. The ATM terminal resource controlsection 225 and the frame relay terminal resource control section 226control (catch/release) the ATM terminal switch resource 221 and theframe relay terminal switch resource 222, respectively.

The ATM terminal resource control section 225 includes ATM callacceptance determination means 227 for determining whether or not an ATMcall from an ATM terminal 201 is to be accepted when the ATM terminal201 tries to use the ATM terminal switch resource 221. The frame relayterminal resource control section 226 includes frame relay callacceptance determination means 228 for determining whether or not aframe relay call from a frame relay terminal 202 is to be accepted whenthe frame relay terminal 202 tries to use the frame relay terminalswitch resource 222.

For the ATM call acceptance determination means 227, a known systemdisclosed, for example, in Japanese Patent Laid-Open Application No.Heisei 4-240683 ("Call Acceptance Determination System for an ATMExchange") can be used as it is, and accordingly, detailed descriptionthereof is omitted herein.

Meanwhile, the frame relay call acceptance determination means 228 mayhave such a functional construction as shown, for example, in FIG. 19.

Referring to FIG. 19, the frame relay call acceptance determinationmeans 228 shown includes virtual band calculation means 231 formultiplying a use requested band requested to set from a frame relayterminal 202 by a predetermined multiplexing rate α (for example, 0.3 to0.5) to convert the use requested band into a use virtual band A1, whichis controlled by the network, subscriber line free band detection means232 for detecting an incoming side free band B1 for the frame relayterminal subscriber lines 204, and outgoing line free band detectionmeans 233 for detecting an outgoing side free band C1 for the outgoinglines for the frame relay terminals (subscriber lines 204 or trunk lines206).

The frame relay call acceptance determination means 228 further includesfirst comparison means 234 for comparing the use virtual band A1calculated by the virtual band calculation means 231 and the incomingside free band B1 detected by the subscriber line free band detectionmeans 232 with each other, and second comparison means 235 for comparingthe use virtual band A1 calculated by the virtual band calculation means231 and the outgoing side free band C1 detected by the outgoing linefree band detection means 233 with each other.

The frame relay call acceptance determination means 228 further includescall acceptance means 236 for performing acceptance processing of aframe relay call from a frame relay terminal 202. The call acceptancemeans 236 accepts a frame relay call from a frame relay terminal 202when the result of comparison by the first comparison means 234 is[incoming side free band B1 for the frame relay terminal subscriberlines 204]>[use virtual band A1] and simultaneously the result ofcomparison by the second comparison means 235 is [outgoing side freeband C1 for the frame relay terminal subscriber lines 204 and framerelay terminal trunk lines 206]>[use virtual band A1].

Due to the construction described above, in the second embodiment, theATM terminal switch resource 221 and the frame relay terminal switchresource 222 are set physically completely separately from each other asthe resources of the ATM exchange 200, and the ATM terminal switchresource 221 and frame relay terminal switch resource 222 are controlledby the ATM terminal resource control section 225 and the frame relayterminal resource control section 226, respectively.

When each of the ATM terminals 201 tries to use the ATM terminal switchresource 221, an acceptance determination of an ATM call from an ATMterminal 201 is performed using the known technique described above bythe ATM call acceptance determination means 227, but when each of theframe relay terminals 202 tries to use the frame relay terminal switchresource 222, an acceptance determination of a frame relay call from aframe relay terminal 202 is performed in accordance with a procedureillustrated in FIG. 20 by the frame relay call acceptance determinationmeans 228 having such a construction as shown in FIG. 19.

In particular, referring to FIG. 20, in the frame relay call acceptancedetermination means 228 shown, the virtual band calculation means 231multiplies a use requested band requested to set from a frame relayterminal 202 by the predetermined multiplexing rate α to convert the userequested band into a use virtual band A1 (step S1), which is controlledby the network.

Further, the subscriber line free band detection means 232 supervisesand detects the incoming side free band B1 for the frame relay terminalsubscriber lines 204, and then the incoming side free band B1 iscompared with the use virtual band A1 by the first comparison means 234(step S2). When the result of comparison is [incoming side free bandB1]>[use virtual band A1], the outgoing line free band detection means233 analyses the outgoing lines for the frame relay terminals (framerelay terminal subscriber lines 204 or frame relay terminal trunk lines206) to supervise and detect the outgoing side free band C1 (step S3).

The outgoing side free band C1 from the outgoing line free banddetection means 233 and the use virtual band A1 are compared with eachother by the second comparison means 235 (step S4), and then, when theresult of comparison is [outgoing side free band C1]>[use virtual bandA1], the call acceptance means 236 accepts the frame relay call from theframe relay terminals 202 (acceptance OK: step S5), assures the usevirtual band A1, and then replaces the incoming side free band B1 andthe outgoing side free band C1 with B1-A1 and C1-A1, respectively.

On the contrary, when the result of comparison by the first comparisonmeans 234 at step S2 is [incoming side free band B1]≦[use virtual bandA1] or when the result of comparison by the second comparison means 235at step S4 is [outgoing side free band C1]≦[use virtual band A1], it isjudged that the use virtual band A1 cannot be assured to either one orboth ones of the incoming side and the outgoing side, and the callacceptance means 236 rejects acceptance of the frame relay call from theframe relay terminal 202 (acceptance NO: step S7).

In this manner, according to the second embodiment, by simply dividingthe resource of the ATM exchange 200, control and call acceptancedetermination regarding the ATM terminal switch resource 221 for the ATMterminals 201 and control and call acceptance determination regardingthe frame relay terminal switch resource 222 for the frame relayterminals 202 can be processed completely independently of each other,and the ATM terminals 201 and the frame relay terminals 202 can beaccommodated very readily into the same ATM exchange 200 and the serviceof accommodating and connecting a frame relay terminal 202 into the ATMexchange 200 can be realized as one of services of the ATM exchange.

It is to be noted that, while, in the second embodiment described above,a user of an ATM terminal 201 or of a frame relay terminal 202 reports ause requested band before it delivers a call, such alternativeconstruction may be employed that a use requested band requested to setfrom an ATM terminal 201 or a frame relay terminal 202 is added as bandinformation to an ATM call from the ATM terminal 201 or to a frame relaycall from the frame relay terminal 202 and transferred to the ATM callacceptance determination means 227 or the virtual band calculation means231 of the frame relay call acceptance determination means 228 togetherwith the ATM call or the frame relay call.

In this instance, the ATM exchange system 220 includes, as shown in FIG.21, a signal apparatus 229 for transferring an ATM call or a frame relaycall from the ATM exchange 200 to the service control section 224 of thecall processor 223.

Between the ATM exchange system 220 having such construction asdescribed above and an ATM terminal 201, such a sequence as illustratedin FIG. 22 is executed when the ATM terminal 201 delivers a request forcall connection. Referring to FIG. 22, a destination telephone number ofthe other party and band information regarding a use requested band areadded to a SETUP (call setting message) signal from the ATM terminal201, and the SETUP signal is transferred to the call processor 223 byway of the ATM exchange 200 and the signal apparatus 229.

In response to the SETUP signal, a CALLPROC (Call Proceeding: a messagefor execution of processing for setting of a call) signal, an ALERT(Alerting: a message of calling a called party) signal and a CONNECT (amessage that the called party has responded) signal are successivelysent out from the call processor 223 to the ATM terminal 201 by way ofthe signal apparatus 229 and the ATM exchange 200.

In this instance, in the call processor 223, numerical interpretationand outgoing path analysis of data in the SETUP signal obtained from thesignal apparatus 229 are performed after the CALLPROC signal isoutputted, and acceptance determination of the ATM call is performed bythe ATM call acceptance determination means 227 regarding the bandinformation added to the SETUP signal as a use requested band. Then, ifthe ATM call acceptance determination means 227 determines that the callshould be accepted, then the call processor 223 outputs an ALERT signal.

Similarly, between the ATM exchange system 220 and a frame relayterminal 202, such a processing sequence as illustrated in FIG. 23 isexecuted when the frame relay terminal 202 delivers a request for callconnection. In particular, referring to FIG. 23, a destination telephonenumber of the other party and band information regarding a use requestedband are added to a SETUP (call setting message) signal from the framerelay terminal 202, and the SETUP signal is transferred to the callprocessor 223 by way of the ATM exchange 200 and the signal apparatus229 after it is converted from a frame relay packet into ATM cells bythe interface unit 151.

In response to the SETUP signal, a CALLPROC signal, an ALERT signal anda CONNECT signal are converted from ATM cells into a frame relay packetby the interface unit 151 and then successively sent out from the callprocessor 223 to the frame relay terminal 202 by way of the signalapparatus 229 and the ATM exchange 200.

In this instance, in the call processor 223, numerical interpretationand outgoing path analysis of data in the SETUP signal obtained by thesignal apparatus 229 are performed after the CALLPROC signal isoutputted, and the band information added to the SETUP signal isinputted as a use requested band to the virtual band calculation means231 of the frame relay call acceptance determination means 228. Thus,acceptance determination of the frame relay call is performed by theframe relay call acceptance determination means 228, and if the framerelay call acceptance determination means 228 determines that the callshould be accepted, then the call processor 223 outputs an ALERT signal.

Since a use requested band is added as band information to an ATM callor a frame relay call and transferred to the call processor 223 by wayof the ATM exchange 200 and the signal apparatus 229 as described above,a user of an ATM terminal 201 or of a frame relay terminal 202 can omitsuch operation as to make a report of a use requested band every timebefore a call is developed, and further enhancement of the service canbe achieved.

d. Third Embodiment

FIG. 24 illustrates a functional construction of frame relay callacceptance determination means according to a third preferred embodimentof the present invention. In the present embodiment, the frame relaycall acceptance determination means 228 of the second embodiment havingsuch construction as described hereinabove with reference to FIG. 19 isreplaced by such frame relay call acceptance determination means 240 asshown in FIG. 24.

Referring to FIG. 24, the frame relay call acceptance determinationmeans 240 shown includes virtual band setting means 241 for setting,when setting of a frame relay call is requested from a frame relayterminal 202, a physical maximum speed (physical line speed) of theframe relay terminal 202 as a use virtual band A2 for the frame relaycall, and band assurance determination means 242 for determining whetheror not a band has been assured already for a same sending subscriber asthe frame relay terminal 202.

The band assurance determination means 242 controls, for example, suchband assurance determination tables 246 as shown in FIG. 27. Referringto FIG. 27, in each of the band assurance determination tables 246shown, presence or absence of an assured band for a frame relay terminal202 of a predetermined sending telephone number to be connected to acircuit of a predetermined circuit number is registered so that, byreferring to a suitable one of the band assurance determination tables246, the band assurance determination means 242 can determine whether ornot a band has been assured already for the same sending subscriber asthe predetermined frame relay terminal 202.

Referring to FIG. 24, the frame relay call acceptance determinationmeans 240 further includes free band detection means 243 for detecting afree band B2 for the frame relay terminal subscriber lines 204 and theframe relay terminal trunk lines 206 for the frame relay terminals 202,comparison means 244 for comparing a use virtual band A2 set by thevirtual band setting means 241 and a free band B2 detected by the freeband detection means 243 with each other, and call acceptance means 245for performing acceptance processing of a frame relay call from a framerelay terminal 202.

The call acceptance means 245 accepts a frame relay call from a framerelay terminal 202 unconditionally when the band assurance determinationmeans 242 determines that a band has been assured already for the samesending subscriber as the frame relay terminal 202. However, when theband assurance determination means 242 determines that no band has beenassured for the same sending subscriber as the frame relay terminal 202and the result of comparison by the comparison means 244 is [free bandB2 for the frame relay terminal subscriber lines 204 and the frame relayterminal trunk lines 206]>[use virtual band A2], the call acceptancemeans 245 assures the use virtual band A2 and accepts the frame relaycall from the frame relay terminal 202.

FIG. 25 illustrates an example of a state of paths when a frame relayterminal 202 is accommodated into an actual ATM exchange network. Asseen from FIG. 25, a frame relay terminal 202 can set paths for aplurality of terminals to enjoy connectionless services.

In this instance, if it is contracted that the traffic amount (use band)from a frame relay terminal 202 to each of a plurality of (for example,four) terminals is, for example, 600 Kbps, if the frame relay terminal202 accesses a plurality of ones of the terminals at a time, then a bandof 2.4 Mbps at the greatest is used. Actually, however, it is impossibleto send out a frame relay packet exceeding the physical maximum speed ofa subscriber line (DS1 line) 204, which interconnects the frame relayterminal 202 and the ATM exchange 200, for example, 1.5 Mbps.

Taking the characteristic just described into consideration, in theframe relay call acceptance determination means 240 of the thirdembodiment, if at least one path from a certain frame relay terminal 202is set on the lines, then a band for the physical maximum speed isassured. On the contrary, even if N paths from a same sending subscriberare set on the same line, a band higher than the physical maximum speedis not assured at all. In the following, an acceptance determinationprocedure for a frame relay call from a frame relay terminal 205 by theframe relay call acceptance determination means 240 in the thirdembodiment will be described with reference to FIG. 26.

In particular, when a frame relay terminal 202 tries to use the framerelay terminal switch resource 222 (when setting of a frame relay callis requested from a frame relay terminal 202), in the frame relay callacceptance determination means 240, the virtual band setting means 241first sets a physical maximum speed (physical line speed) of the framerelay terminal 202 as a use virtual band A2 for the frame relay call(step S11).

Then, the band assurance determination means 242 refers to the bandassurance determination tables 246 to determine whether or not a bandhas been assured already on the frame relay terminal switch resource 222for the same sending subscriber as the frame relay terminal 202 fromwhich the request for setting of a call has been developed (step S12).When it is determined at step S12 that a band has been assured already,the control sequence advances to step S15, at which the frame relay callfrom the frame relay terminal 202 is accepted unconditionally by thecall acceptance means 245.

On the contrary if it is determined at step S12 that no band has beenassured as yet for the same sending subscriber as the frame relayterminal 202, then a result of supervision and detection of the freeband B2 for the frame relay terminal subscriber lines 204 and the framerelay terminal trunk lines 206 by the free band detection means 243 isreceived and compared with the use virtual band A2 (physical maximumspeed) by the comparison means 244 (step S13).

When the result of comparison is [free band B2]>[use virtual band A2],the use virtual band A2 is assured and the free band B2 is replaced byB2-A2 (step S14), and then the frame relay call from the frame relayterminal 202 is accepted by the call acceptance means 245 (acceptanceOK: step S15).

On the contrary, when the result of comparison by the comparison means244 at step S13 is [free band B2]≦[use virtual band A2], it isdetermined that the use virtual band A2 cannot be assured on the framerelay terminal switch resource 222, and the call acceptance means 245rejects the frame relay call from the frame relay terminal 202(acceptance NG: step 816).

In this manner, according to the third embodiment, similar effects tothose of the second embodiment can be obtained. Further, where at leastone path from a certain frame relay terminal 202 is set on the lines,since a band for the physical maximum speed is assured so that a bandfor a speed higher than the physical maximum speed cannot be assuredeven if a plurality of paths from the same sending subscriber are set onthe same line, each frame relay terminal 202 is permitted to make acontract for a speed higher than a physical maximum speed of the framerelay terminal 202 as seen from FIG. 25. Accordingly, even where a framerelay terminal 202 is accommodated into the ATM exchange 200 so that aframe relay service may be enjoyed, a path for a frame relay packet canbe set on the ATM exchange network while adopting the same conditions asof existing frame relay services, and besides, the resource can beutilized effectively.

e. Fourth Embodiment

FIG. 28 shows the construction of an ATM exchange system as a fourthpreferred embodiment of the present invention. Also in the presentembodiment, similarly as in the second and third embodiments describedhereinabove, an ATM exchange 200 which constitutes an ATM exchangesystem 220 accommodates a plurality of ATM terminals 201 by way ofrespective ATM terminal subscriber lines 203 and accommodates aplurality of frame relay terminals 202 by way of respective frame relayterminal subscriber lines 204. In the present embodiment, however, theresource (free band) of the ATM exchange 200 is shared commonly by theATM terminals and the frame relay terminals, and trunk lines 211 of theATM exchange 200 are not separated for the ATM terminals and the framerelay terminals. It is to be noted that those reference numerals in FIG.28 which are common to those used for the preceding embodiments denotelike components, and overlapping description thereof is omitted hereinto avoid redundancy.

Referring to FIG. 28, the call processor 223 in the ATM exchange system220 includes an ATM terminal subscriber resource control section 251 forcontrolling an ATM terminal subscriber access resource (refer to anarrow mark 1 in FIG. 28) when an ATM call from an ATM terminal 201 isinputted to the ATM exchange 200 by way of a respective ATM terminalsubscriber line 203 and then sent out to another ATM terminal 201 by wayof another respective ATM terminal subscriber line 203, and a framerelay terminal subscriber resource control section 252 for controlling aframe relay terminal subscriber access resource (refer to an arrow mark2 of FIG. 28) when a frame relay call from a frame relay terminal 202 isinputted to the ATM exchange 200 by way of a respective frame relayterminal subscriber lines 204 and the interface unit 151 and then sentout to another frame relay terminal 202 by way of another respectiveframe relay terminal subscriber line 204 and the interface unit 151.

The call processor 223 further includes a network resource controlsection 253 for controlling a network common resource (refer to an arrowmark 3 or 4 in FIG. 28) when an ATM call from an ATM terminal 201 or aframe relay call from a frame relay terminal 202 is inputted to the ATMexchange 200 by way of an ATM terminal subscriber line 203 or a framerelay terminal subscriber line 204 and then sent out to a trunk line211.

The ATM terminal subscriber resource control section 251 includes ATMcall acceptance determination means 254 for determining whether or notan ATM call from an ATM terminal 201 should be accepted when the ATMterminal 201 tries to use the ATM terminal subscriber access resource.Meanwhile, the frame relay terminal subscriber resource control section252 includes frame relay call acceptance determination means 255 fordetermining whether or not a frame relay call from a frame relayterminal 202 should be accepted when the frame relay terminal 202 triesto use the frame relay terminal subscriber access resource. Further, thenetwork resource control section 253 includes common resource callacceptance determination means 256 for determining whether or not an ATMcall from an ATM terminal 201 or a frame relay call from a frame relayterminal 202 should be accepted when the ATM terminal 201 or the framerelay terminal 202 tries to use the network common resource. It is to benoted that, since a known technique similar to that employed in thesecond embodiment can be used as it is for the ATM call acceptancedetermination means 254, detailed description of the same is omittedherein.

The frame relay call acceptance determination means 255 may have such afunctional construction as illustrated, for example, in FIG. 29.

Referring to FIG. 29, the frame relay call acceptance determinationmeans 255 shown includes virtual band calculation means 261 formultiplying a use requested band requested to set from a frame relayterminal 202 by a predetermined multiplexing rate α (for example, 0.3 to0.5) to convert the use requested band into a use virtual band A3, whichis controlled by the network, incoming side subscriber line free banddetection means 262 for detecting a free band B3 for the frame relayterminal subscriber lines 204, and outgoing side subscriber line freeband detection means 263 for detecting a free band C3 for the framerelay terminal subscriber lines 204.

The frame relay call acceptance determination means 255 further includesfirst comparison means 264 for comparing a use virtual band A3calculated by the virtual band calculation means 261 and a free band B3detected by the incoming side subscriber line free band detection means262 with each other, and second comparison means 265 for comparing a usevirtual band A3 calculated by the virtual band calculation means 261 anda free band C3 detected by the outgoing side subscriber line free banddetection means 263 with each other.

The frame relay call acceptance determination means 255 further includescall acceptance means 266 for performing acceptance processing of aframe relay call from a frame relay terminal 202. The call acceptancemeans 266 accepts a frame relay call from a frame relay terminal 202when the result of comparison by the first comparison means 264 is [freeband B3 of the frame relay terminal subscriber line 204]>[use virtualband A3] and when the result of comparison by the second comparisonmeans 265 is [free band C3 of the frame relay terminal subscriber line204]>[use virtual band A3].

Meanwhile, the common resource call acceptance determination means 256may have such a functional construction as illustrated, for example, inFIG. 30.

Referring to FIG. 30, the common resource call acceptance determinationmeans 256 shown includes virtual band calculation means 267 formultiplying a use requested band requested to set from an ATM terminal201 or a frame relay terminal 202 by a predetermined multiplexing rate β(for example, 0.7 to 1.0) to convert the use requested band into a usevirtual band A4 which is controlled by the network, and common resourcefree band detection means 268 for detecting a free band B4 on thenetwork common resource of the ATM exchange 200.

The common resource call acceptance determination means 256 furtherincludes comparison means 269 for comparing a use virtual band A4calculated by the virtual band calculation means 267 and a free band B4detected by the common resource free band detection means 268 with eachother, and call acceptance means 270 for accepting an ATM call from anATM terminal 201 or a frame relay call from a frame relay terminal 202when the result of comparison by the comparison means 269 is [free bandB4 on the common resource in the network]>[use virtual band A4].

Due to the construction described above, in the fourth embodiment, theATM terminal resource and the frame relay terminal resource are setcommonly on the resource of the ATM exchange 200, and the ATM terminalsubscriber access resource indicated by the arrow mark 1 in FIG. 28 andthe frame relay terminal subscriber access resource indicated by thearrow mark 2 in FIG. 28 are controlled by the ATM terminal subscriberresource control section 251 and the frame relay terminal subscriberresource control section 252, respectively, while the network commonresource indicated by the arrow marks 3 and 4 in FIG. 28 is controlledby the network resource control section 253.

Then, when one of the ATM terminals 201 tries to use the ATM terminalsubscriber access resource, the ATM call acceptance determination means254 performs acceptance determination of the ATM call from the ATMterminals 201 using the known technique described above. But when one ofthe frame relay terminals 202 tries to use the frame relay terminalsubscriber access resource, the frame relay call acceptancedetermination means 255 having such a construction as illustrated inFIG. 29 performs acceptance determination of the frame relay call fromthe frame relay terminals 202 in accordance with the procedureillustrated in FIG. 31. On the other hand, when an ATM terminal 201 or aframe relay terminal 202 tries to use the network common resource, thecommon resource call acceptance determination means 256 having such aconstruction as illustrated in FIG. 30 performs acceptance determinationof the ATM call from the ATM terminal 201 or of the frame relay callfrom the frame relay terminals 202 in accordance with the procedureillustrated in FIG. 32.

In particular, referring to FIG. 31, in the frame relay call acceptancedetermination means 255, the virtual band calculation means 261 firstmultiplies a use requested band requested to set from a frame relayterminal 202 by the predetermined multiplexing rate α to convert the userequested band into a use virtual band A3 (step S21), which iscontrolled by the network.

Further, the incoming side subscriber line free band detection means 262supervises and detects a free band B3 for the frame relay terminalsubscriber lines 204, and the free band B3 is compared with the usevirtual band A3 by the first comparison means 264 (step S22).

When the result of comparison is [free band B3]>[use virtual band A3],the frame relay call acceptance determination means 255 determineswhether or not the outgoing line from the ATM exchange 200 upon settingof a call from the frame relay terminal 202 in this instance is a trunkline 211 (step S23). If the outgoing line is a trunk line 211, thensince the network common resource (indicated at the arrow mark 4 in FIG.28) should be used, the control sequence advances to processing by thecommon resource call acceptance determination means 256 which will behereinafter described with reference to FIG. 32 (step S28).

On the other hand, if it is determined at step S23 that the outgoingline is not any trunk line 211, since the frame relay terminalsubscriber access resource indicated by the arrow mark 2 in FIG. 28should be used, the outgoing side subscriber line free band detectionmeans 263 supervises and detects a free band C3 for the frame relayterminal subscriber lines 204, and the free band C3 is compared with theuse virtual band A3 by the second comparison means 265 (step S24).

When the result of comparison is [free band C3]>[use virtual band A3],the call acceptance means 266 accepts the frame relay call from theframe relay terminal 202 (acceptance OK: step S25), and the use virtualband A3 is assured and the free band B3 and free band C3 are replaced byB3-A3 and C3-A3, respectively, (step S26).

When the result of comparison at step S22 by the first comparison means264 is [free band B3]≦[use virtual band A3] or the result of comparisonat step S24 by the second comparison means 265 is [free band C3]≦[usevirtual band A3], it is determined that the use virtual band A3 cannotbe assured at either one or neither one of the incoming side and theoutgoing side of the frame relay terminal subscriber line 204, and thecall acceptance means 266 rejects acceptance of the frame relay callfrom the frame relay terminal 202 (acceptance NG: step S27).

Meanwhile, referring to FIG. 32, in the common resource call acceptancedetermination means 256, the virtual band calculation means 267multiplies the use requested band requested to set from an ATM terminal201 or a frame relay terminal 202 by the predetermined multiplexing rateβ to convert the use requested band into a use virtual band A4 (stepS31), which is controlled by the network.

Further, the common resource free band detection means 268 supervisesand detects a free band B4 on the network common resource of the ATMexchange 200, and the free band B4 is compared with the use virtual bandA4 by the comparison means 269 (step S32).

Then, when the result of comparison is [free band B4]>[use virtual bandA4], the call acceptance means 270 accepts the ATM call from the ATMterminal 201 or the frame relay call from the frame relay terminal 202(acceptance OK: step S33), and the use virtual band A4 is assured andthe free band B4 is replaced by B4-A4 (step S34).

When the result of comparison at step S32 by the comparison means 269 is[free band B4]≦[use virtual band A4], it is determined that the networkcommon resource does not have a free area for the use virtual band A4and consequently the use virtual band A4 cannot be assured, and the callacceptance means 270 does not accept the ATM call from the ATM terminal201 or the frame relay call from the frame relay terminal 202(acceptance NG: step S35).

In this manner, according to the fourth embodiment, control and callacceptance determination of the ATM terminal subscriber access resourceand control and call acceptance determination of the frame relayterminal subscriber access resource are performed by the ATM callacceptance determination means 254 and the frame relay call acceptancedetermination means 255, respectively, while control and call acceptancedetermination of the network common resource are processed in accordancewith an algorithm (same controlling method) common to both of an ATMcall from an ATM terminal 201 and a frame relay call from a frame relayterminal 202 by the common resource call acceptance determination means256. Consequently, even where the resource of the ATM exchange 200 isshared by both of the resource for the ATM terminals and the resourcefor the frame relay terminals, the ATM terminals 201 and the frame relayterminals 202 can be accommodated very readily into the same ATMexchange 200, and similarly as in the second embodiment, the service foraccommodating and connecting the frame relay terminals 202 into and tothe ATM exchange 200 can be realized as one of services of the ATMexchange.

It is to be noted that, while, in the fourth embodiment described above,a user of an ATM terminal 201 or of a frame relay terminal 202 reports ause requested band before a call is developed, such an alternativeconstruction may be employed that a use requested band requested to setfrom an ATM terminal 201 or a frame relay terminal 202 is added as bandinformation to the ATM call from the ATM terminal 201 or to the framerelay call from the frame relay terminal 202 and transferred to the ATMcall acceptance determination means 254, the virtual band calculationmeans 261 of the frame relay call acceptance determination means 255 orthe virtual band calculation means 267 of the common resource callacceptance determination means 256 together with the ATM call or theframe relay call.

In this instance, similarly to the case described hereinabove withreference to FIG. 21 in connection with the second embodiment, the ATMexchange system 220 includes a signal apparatus 229 for transferring anATM call or a frame relay call from the ATM exchange 200 to the servicecontrol section 224 of the call processor 223. Consequently, also in thepresent fourth embodiment, a user of an ATM terminal 201 or of a framerelay terminal 202 can omit the operation to report a use requested bandevery time before a call is developed, and further enhancement of theservice can be realized.

f. Fifth Embodiment

FIG. 33 shows the construction of an ATM exchange system as a fifthpreferred embodiment of the present invention. As seen from FIG. 33,also the ATM exchange system 220 in the fifth embodiment is constructedsubstantially in a similar manner as that in the fourth embodiment shownin FIG. 28, but in the present fifth embodiment, a portion thereofcorresponding to the common resource call acceptance determination means256 (refer to FIG. 28) in the fourth embodiment is constituted from twoseparate elements including common resource ATM call acceptancedetermination means 271 for determining whether or not an ATM call froman ATM terminal 201 should be accepted when the ATM terminal 201 triesto use the network common resource, and common resource frame relay callacceptance determination means 272 for determining whether or not aframe relay call from a frame relay terminal 202 should be accepted whenthe frame relay terminal 202 tries to use the network common resource.

It is to be noted that, in FIG. 33, like reference numerals to thosedescribed hereinabove denote like elements, and accordingly, overlappingdescription of them will be omitted herein to avoid redundancy.

Each of the common resource ATM call acceptance determination means 271and the common resource frame relay call acceptance determination means272 may be means having a substantially similar functional constructionto that of the common resource call acceptance determination means 256described hereinabove with reference to FIG. 30.

It is to be noted, however, that, in the present embodiment, themultiplexing rate by which a use requested band requested to set from anATM terminal 201 is multiplied by the virtual band calculation means 267constituting the common resource ATM call acceptance determination means271 and the multiplexing rate by which a use requested band requested toset from a frame relay terminal 202 is multiplied by the virtual bandcalculation means 267 constituting the common resource frame relay callacceptance determination means 272 are set in accordance withcharacteristics of them. In particular, a first multiplexing rate β1(for example, 0.7 to 1.0) for a use requested band requested to set froman ATM terminal 201 and a second multiplexing rate β2 (for example, 0.5to 1.0) for a use requested band requested from a frame relay terminal202 are set in advance in the virtual band calculation means 267.

Due to the construction described above, in the fifth embodiment, callacceptance determination processing is performed in accordance with suchseparate algorithms as illustrated in FIGS. 34 and 35 for an ATM callfrom an ATM terminal 201 and a frame relay call from a frame relayterminal 202, respectively, on the network common resource by the thecommon resource ATM call acceptance determination means 271 and thecommon resource frame relay call acceptance determination means 272.

In particular, referring to FIG. 34, in the common resource ATM callacceptance determination means 271, the virtual band calculation means267 first multiplies a use requested band requested to set from an ATMterminal 201 by the first multiplexing rate β1 to convert the userequested band into a use virtual band A4 (step S41), which iscontrolled by the network.

Further, the common resource free band detection means 268 supervisesand detects a free band B4 on the network common resource of the ATMexchange 200, and the free band B4 is compared with the use virtual bandA4 by the comparison means 269 (step S42).

Then, when the result of comparison is [free band B4]>[use virtual bandA4], the call acceptance means 270 accepts the frame relay call from theATM call from the ATM terminal 201 (acceptance OK: step S43), and theuse virtual band A4 is assured and the free band B4 is replaced by B4-A4(step S44).

When the result of comparison at step S42 by the comparison means 269 is[free band B4]≦[use virtual band A4], it is determined that the networkcommon resource does not have a free area for the use virtual band A4and the use virtual band A4 cannot be assured, and the call acceptancemeans 270 rejects acceptance of the ATM call from the ATM terminal 201(acceptance NG: step S45).

Quite similarly, in the common resource frame relay call acceptancedetermination means 272, the virtual band calculation means 267 firstmultiplies, as seen from FIG. 35, a use requested band requested to setfrom a frame relay terminal 202 by the first multiplexing rate β1 toconvert the use requested band into a use virtual band A4 (step S51),which is controlled by the network.

Further, the common resource free band detection means 268 supervisesand detects a free band B4 on the network common resource of the ATMexchange 200, and the free band B4 is compared with the use virtual bandA4 by the comparison means 269 (step S52).

Then, when the result of comparison is [free band B4]>[use virtual bandA4], the call acceptance means 270 accepts the frame relay call from theframe relay call from the frame relay terminal 202 (acceptance OK: stepS53), and the use virtual band A4 is assured and the free band B4 isreplaced by B4-A4 (step S54).

When the result of comparison at step S52 by the comparison means 269 is[free band B4]≦[use virtual band A4], it is determined that the networkcommon resource does not have a free area for the use virtual band A4and the use virtual band A4 cannot be assured, and the call acceptancemeans 270 rejects acceptance of the frame relay call from the framerelay terminal 202 (acceptance NG: step S55).

In this manner, according to the fifth embodiment, similar effects tothose of the fourth embodiment can be achieved. Further, since thecommon resource call acceptance determination means 256 in the fourthembodiment is divided into the common resource ATM call acceptancedetermination means 271 and the common resource frame relay callacceptance determination means 272, call acceptance determinationprocessing is performed in accordance with the separate algorithms foran ATM call from an ATM terminal 201 and a frame relay call from a framerelay terminal 202 on the network common resource, and consequently,call acceptance determination processing can be performed for an ATMcall and a frame relay call using the first multiplexing rate β1 and thesecond multiplexing rate β2, respectively, which conform to therespective characteristics of them. Further, since a band for paths forall of the frame relay terminals is assured as a virtual band, thecommon resource can be utilized effectively.

g. Sixth Embodiment

FIG. 36 shows a functional construction of common resource frame relaycall acceptance determination means as a sixth preferred embodiment ofthe present invention. In the present sixth embodiment, the commonresource frame relay call acceptance determination means 272 in thefifth embodiment is constructed in such a manner as shown in FIG. 36.

Referring to FIG. 36, the common resource frame relay call acceptancedetermination means 272 shown includes virtual band setting means 281for setting a physical maximum speed (physical line speed) of a framerelay terminal 202 as a use virtual band A5 for a frame relay call whensetting of a frame relay call is requested from the frame relay terminal202, and band assurance determination means 282 for determining whetheror not a band has been assured already for a same sending subscriber asthe frame relay terminals 202 on the network common resource.

The band assurance determination means 282 controls, similarly to theband assurance determination means 242 described hereinabove inconnection with the third embodiment, such band assurance determinationtables 246 as, for example, shown in FIG. 27 and refers to the bandassurance determination tables 246 to determine whether or not a bandhas been assured already for the same sending subscriber as thepredetermined frame relay terminal 202 on the network common resource.

The common resource frame relay call acceptance determination means 272further includes common resource free band detection means 283 fordetecting a free band B5 on the network common resource of the ATMexchange 200, comparison means 284 for comparing a use virtual band A5set by the virtual band setting means 281 and a free band B5 detected bythe common resource free band detection means 283 with each other, andcall acceptance means 285 for performing acceptance processing of aframe relay call from a frame relay terminal 202 using the commonresource.

The call acceptance means 285 accepts, when the band assurancedetermination means 282 determines that a band has been assured alreadyfor a same sending subscriber as a frame relay terminal 202, the framerelay call from the frame relay terminal 202 unconditionally. However,when the band assurance determination means 282 determines that no bandhas been assured as yet for the same sending subscriber as the framerelay terminal 202 and the result of comparison by the comparison means284 is [free band B5 on the common resourse in the network]>[use virtualband A5], the call acceptance means 285 assures the use virtual band A5and accepts the frame relay call from the frame relay terminal 202.

By the way, also in the present sixth embodiment, taking thecharacteristic described hereinabove with reference to FIG. 25 inconnection with the third embodiment into consideration, if at least onepath from a certain frame relay terminal 202 is set on the lines, a bandcorresponding to a physical maximum speed of the frame relay terminal202 is assured, and on the contrary, if N paths from a same sendingsubscriber are set on the same lines, a band for a speed higher than thephysical maximum speed may not be assured.

In the following, an acceptance determination procedure for a framerelay call from a frame relay terminal 202 by the common resource framerelay call acceptance determination means 272 in the sixth embodimentwill be described with reference to FIG. 37.

In particular, when a frame relay terminal 202 tries to use the networkcommon resource, in the common resource frame relay call acceptancedetermination means 272, the virtual band setting means 281 first setsthe physical maximum speed (physical line speed) of the frame relayterminal 202 as a use virtual band A5 for the frame relay call (stepS61) as seen from FIG. 37.

Then, the band assurance determination means 282 refers to the bandassurance determination tables 246 to determine whether or not a bandhas been assured already for a same sending subscriber as the framerelay terminal 202, from which the present request for setting for acall has been developed, on the network common resource (step S62). Whenit is determined at step S62 that a band has been assured already, thecontrol sequence advances to step S65, at which the frame relay callfrom the frame relay terminal 202 is accepted unconditionally by thecall acceptance means 285.

On the other hand, when it is determined at step S62 that no band hasbeen assured as yet for the same sending subscriber as the frame relayterminal 202, the result of supervision and detection of a free band B5on the network common resource by the common resource free banddetection means 283 is received, and the free band B5 and the usevirtual band A5 (physical maximum speed) are compared with each other bythe comparison means 284 (step S63).

When the result of comparison is [free band B5]>[use virtual band A5],the use virtual band A5 is assured and the free band B5 is replaced byB5-A5 (step S64), and then the frame relay call from the frame relayterminal 202 is accepted by the call acceptance means 285 (acceptanceOK: step S65).

On the contrary, when the result of comparison at step S63 by thecomparison means 284 is [free band B5]≦[use virtual band A5], it isdetermined that the use virtual band A5 cannot be assured on the networkcommon resource, and the call acceptance means 285 rejects acceptance ofthe frame relay call from the frame relay terminal 202 (acceptance NG:step S66).

In this manner, according to the sixth embodiment, similar effects tothose of the fourth and fifth embodiments are achieved. Further,similarly to the third embodiment, when at least one path from a certainframe relay terminal 202 is set on the lines, a band corresponding to aphysical maximum speed of the frame relay terminal 202 is assured, andeven if a plurality of paths from a same sending subscriber are set onthe same lines, a band for a speed higher than the physical maximumspeed is not assured. Consequently, each frame relay terminal 202 ispermitted to make a contract for a speed higher than a physical maximumspeed of the frame relay terminal 202. Accordingly, even where a framerelay terminal 202 is accommodated into the ATM exchange 200 so that aframe relay service may be enjoyed, a path for a frame relay packet canbe set on the ATM exchange network while adopting the same conditions asthose of existing frame relay services, and besides, resources can beutilized effectively.

h. Seventh Embodiment

FIG. 38 shows a functional construction of common resource frame relaycall acceptance determination means as a seventh preferred embodiment ofthe present invention. In the present seventh embodiment, the commonresource frame relay call acceptance determination means 272 in thesixth embodiment constructed in such a manner as seen from FIG. 36 isreplaced by such common resource frame relay call acceptancedetermination means 300 as shown in FIG. 38.

Referring to FIG. 38, the common resource frame relay call acceptancedetermination means 300 shown includes virtual band setting means 301for setting a use requested band requested to set for a frame relay callfrom a frame relay terminal 202 as a use virtual band A6 for the framerelay call, and band assurance determination means 302 for determiningwhether or not a band has been assured already for a same sendingsubscriber as a frame relay terminal 202 on a network common resource.

The common resource frame relay call acceptance determination means 300further includes common resource free band detection means 303 fordetecting a free band B6 on the network common resource of an ATMexchange 200, and first comparison means 304 for comparing, when it isdetermined by the band assurance determination means 302 that no bandhas been assured for a same sending subscriber as a frame relay terminal202, a use virtual band A6 set by the virtual band setting means 301with a free band B6 detected by the common resource free band detectionmeans 303.

The common resource frame relay call acceptance determination means 300further includes assured band extraction means 305 for extracting, whenit is determined by the band assurance determination means 302 that aband has been assured for a same sending subscriber as a frame relayterminal 202, an assured band a which has been assured already for theframe relay terminal 202, and second comparison means 306 for comparingan assured band a extracted by the assured band extraction means 305with a physical maximum speed of the frame relay terminal 202.

The common resource frame relay call acceptance determination means 300further includes third comparison means 307 for comparing, when theresult of comparison by the second comparison means 306 is [assured banda]≦[physical maximum speed of the frame relay terminal 202], the suma+A6 of the assured band a and the use virtual band A6 requested fromthe frame relay terminal 202 with the physical maximum speed of theframe relay terminal 202.

The common resource frame relay call acceptance determination means 300further includes remaining available band calculation means 308 forsubtracting, when the result of comparison by the third comparison means307 is [sum a+use virtual band A6]>[physical maximum speed of the framerelay terminal 202], the assured band a from the physical maximum speedof the frame relay terminal 202 to calculate a remaining available bandC6.

The common resource frame relay call acceptance determination means 300further includes fourth comparison means 309 for comparing a remainingavailable band C6 calculated by the remaining available band calculationmeans 308 with a free band B6 detected by the common resource free banddetection means 303, and fifth comparison means 310 for comparing, whenthe result of comparison by the third comparison means 307 is [suma+A6]≦[physical maximum speed of the frame relay terminal 202], the usevirtual band A6 set by the virtual band setting means 301 and the freeband B6 detected by the common resource free band detection means 303with each other.

The common resource frame relay call acceptance determination means 300further includes call acceptance means 311 for performing acceptanceprocessing of a frame relay call from a frame relay terminal 202 whichuses a common resource.

The call acceptance means 311 assures, when the result of comparison bythe first comparison means 304 or the fifth comparison means 310 is[free band B6 on the common resource]>[use virtual band A6], the usevirtual band A6 and accepts the frame relay call from the frame relayterminal 202, but when the result of comparison by the fourth comparisonmeans 309 is [free band B6 on the common resource]>[remaining availableband C6], the call acceptance means 311 assures the remaining availableband C6 and accepts the frame relay call from the frame relay terminal202. On the other hand, when the result of comparison by the secondcomparison means 306 is [assured band a]>[physical maximum speed of theframe relay terminal 202], the call acceptance means 311 accepts theframe relay call from the frame relay terminal 202 unconditionally.

The common resource frame relay call acceptance determination means 300further includes a use band table 312 which controls and stores, foreach frame relay terminal 202 connected to the ATM exchange 200 by wayof a respective frame relay terminal subscriber line 204, a physicalmaximum speed (physical line speed) of the frame relay terminal 202 anda sum total (total band) of use requested bands which have beenrequested to set by the frame relay terminal 202 by the present point oftime.

In the use band table 312, a physical maximum speed and a total band areparticularly registered for a frame relay terminal 202 of apredetermined sending telephone number connected to a predeterminedcircuit number as seen from FIGS. 40, 42 and 43. The band assurancedetermination means 302 refers to the use band table 312 to determinewhether or not a band has been assured already for a same sendingsubscriber as a predetermined frame relay terminal 202.

Meanwhile, the assured band extraction means 305 extracts a total bandof the use band table 312 as the band a assured already for the framerelay terminal 202, and the physical maximum speed of the frame relayterminal 202 to be used by the second comparison means 306, the thirdcomparison means 307 and the remaining available band calculation means308 is read out from the use band table 312.

Due to the construction described above, in the seventh embodiment, whena frame relay terminal 202 tries to use the network common resource,acceptance determination of a frame relay call from the frame relayterminal 202 is performed in accordance with a procedure illustrated inFIG. 39 by the common resource frame relay call acceptance determinationmeans 300 having such a construction as shown in FIG. 38.

In particular, referring to FIG. 39, in the common resource frame relaycall acceptance determination means 300, the virtual band setting means301 first sets a use requested band requested to set for a frame relaycall from a frame relay terminal 202 as a use virtual band A6 for theframe relay call (step S71).

Then, the band assurance determination means 302 refers to the use bandtable 312 and determines whether or not a band has been assured alreadyfor a same sending subscriber as the frame relay terminal 202, fromwhich the request for setting of a call has been developed, on thenetwork common resource (step S72).

When it is determined at step S72 that a band has been assured already,the assured band extraction means 305 refers to the use band table 312and extracts a total band of the frame relay terminal 202 registered onthe use band table 312 as an assured band a assured already for theframe relay terminal 202 (step S73), and then the thus extracted assuredband a is compared with the physical maximum speed of the frame relayterminal 202 read out from the use band table 312 by the secondcomparison means 306 (step S74).

When the result of comparison is [assured band a]≦[physical maximumspeed of the frame relay terminal 202], the third comparison means 307compares the sum a +A6 of the assured band a and the use virtual band A6with the physical maximum speed of the frame relay terminal 202 read outfrom the use band table 312 (step S75), but when the result ofcomparison is [sum a+A6]>[physical maximum speed of the frame relayterminal 202], the remaining available band calculation means 308subtracts the assured band a from the physical maximum speed of theframe relay terminal 202 to calculate a remaining available band C6(step S76).

Thereafter, the fourth comparison means 309 compares the free band B6 onthe network common resource detected by the common resource free banddetection means 303 with the remaining available band C6 (step S78), andwhen the result of comparison is [free band B6]>[remaining availableband C6], the remaining available band C6 is assured and the free bandB6 is replaced by B6-C6 (step S79). Then, the frame relay call from theframe relay terminal 202 is accepted by the call acceptance means 311(acceptance OK: step S80). Consequently, a band for a physical maximumspeed is assured for the frame relay terminal 202.

On the other hand, when the result of comparison at step S78 by thefourth comparison means 309 is [free band B6]≦[remaining available bandC6], it is determined that the remaining available band C6 cannot beassured on the network common resource, and the call acceptance means311 rejects the frame relay call from the frame relay terminal 202(acceptance NG: step S81).

Further, when the result of comparison at step S75 by the thirdcomparison means 307 is [sum a+A6]≦[physical maximum speed of the framerelay terminal 202], the fifth comparison means 310 compares the freeband B6 on the network common resource detected by the common resourcefree band detection means 303 with the use virtual band A6 (step S82).

When the result of comparison at step S75 is [free band B6]>[use virtualband A6], the use virtual band A6 is assured and the free band B6 isreplaced by B6-A6 (step S83), and the frame relay call from the framerelay terminal 202 is accepted by the call acceptance means 311 (stepS80).

When the result of comparison at step S82 by the fifth comparison means310 is [free band B6]≦[use virtual band A6], it is determined that theuse virtual band A6 cannot be assured on the network common resource,and the call acceptance means 311 rejects acceptance of the frame relaycall from the frame relay terminal 202 (step S81).

On the other hand, when the result of comparison at step S74 by thesecond comparison means 306 is [assured band a]>[physical maximum speedof the frame relay terminal 202], the call acceptance means 311 acceptsthe frame relay call from the frame relay terminal 202 unconditionally(step S80).

Further, when the band assurance determination means 302 refers, at step72, to the use band table 312 and determines that no band has beenassured as yet for the same sending subscriber as the frame relayterminal 202, the first comparison means 304 compares the free band B6on the network common resource detected by the common resource free banddetection means 303 with the use virtual band A6 set by the virtual bandsetting means 301 (step S84).

When the result of comparison is [free band B6]>[use virtual band A6],the use virtual band A6 is assured and the free band B6 is replaced byB6-A6 (step S83), and the call acceptance means 311 accepts the framerelay call from the frame relay terminal 202 (step S80).

On the contrary, when the result of comparison at step S84 by the firstcomparison means 304 is [free band B6]≦[use virtual band A6], it isdetermined that the use virtual band A6 cannot be assured on the networkcommon resource, and the call acceptance means 311 rejects acceptance ofthe frame relay call from the frame relay terminal 202 (step S81).

In this manner, according to the seventh embodiment, for an ascendingpath from a frame relay terminal subscriber line 204 for a frame relayterminal 202, a physical maximum speed is had as a fixed value on eachphysical transmission line, and call acceptance determination processingis performed while connection of a path of a speed lower than thephysical maximum speed is assured on the total band.

In particular, call acceptance determination processing is performedsuch that, when the sum total (total band A6+a) of use requested bandswhich have been requested to set before the present point of time fromthe frame relay terminal 202 is lower than the physical maximum speed, aband is assured with the total value, but when the total band becomeshigher than the physical maximum speed, a band is assured at thephysical maximum speed.

Accordingly, the common resource of the ATM exchange 200 can be utilizedfurther effectively.

A concrete example of such band assurance upon allocation within thephysical maximum speed in the seventh embodiment will be described withreference to FIGS. 41 to 43. In FIGS. 41 to 43, a case is illustratedwherein a request for connection of a use requested band of 600 kbpsfrom a frame relay terminal of the sending telephone number 2-6141 toanother frame relay terminal of the receiving telephone number 3-1111 asa new path has been developed in a condition wherein such paths asindicated by solid lines in FIG. 41 have been set already.

In this instance, a band is not assured newly for the line 1 since thetotal band of it is higher than the physical maximum speed of 1.5 Mbpsas seen from FIG. 42. Meanwhile, since a path of a band of 600 kbps hasbeen set already as seen in FIG. 43 for the line 3, even if a path of aband of 600 kbps is set further, the total band is 1.2 Mbps and does notexceed the physical maximum speed of 1.5 Mbps, a band of 600 kbps isassured newly.

Further, in the seventh embodiment, since the physical maximum speed(physical line speed) and the total band requested to set before thepresent point of time are controlled and stored for each frame relayterminal 202 by the use band table 312, the total band of the use bandtable 312 can be used as the assured band a of the frame relay terminal202. In addition, the physical maximum speed of the frame relay terminal202 which is required for comparison or for calculation of the remainingavailable band C6 can be read out from the use band table and used, andconsequently, it is advantageous in that control of data and calculationby the means can be performed efficiently.

It is to be noted that, while, in the seventh embodiment describedabove, a user of a frame relay terminal 202 reports a use requested bandbefore a call is developed, such an alternative construction may beemployed that a use requested band requested to set from a frame relayterminal 202 is added as band information to the frame relay call fromthe frame relay terminal 202 and transferred to the virtual band settingmeans 301 of the common resource frame relay call acceptancedetermination means 300 together with the frame relay call.

In this instance, similarly to the case described hereinabove withreference to FIG. 21 in connection with the second embodiment, the ATMexchange system 220 includes a signal apparatus 229 for transferring aframe relay call from the ATM exchange 200 to the service controlsection 224 of the call processor 223. Consequently, also in the presentseventh embodiment, a user of a frame relay terminal 202 can omit theoperation to report a use requested band every time before a call isdeveloped, and further enhancement of the service can be realized.

The present invention is not limited to the specifically describedembodiment, and variations and modifications may be made withoutdeparting from the scope of the present invention.

What is claimed is:
 1. A variable length frame exchanging method by a fixed length cell handling exchange which handles fixed length cells each including a first logic channel information, a logic path information and a data section and to which a terminal adapted for a data communication using a variable length frame including a second logic channel information is connected by a transmission line having at least one channel, the method comprising the steps of:disassembling the variable length frame transmitted from said terminal into fixed length cells; translating the second logic channel information in the variable length frame into the first logic channel information and the logic path information for the fixed length cells; and providing the first logic channel information and the logic path information obtained in said translating step for the fixed length cells obtained in said disassembling step and inputting the fixed length cells with the first logic channel information and the logic path information to said exchange.
 2. A variable length frame exchanging method by a fixed length cell handling exchange which handles fixed length cells each including a first logic channel information, a logic path information and a data section and to which a terminal adapted for a data communication using a variable length frame including a second logic channel information is connected by a transmission line having at least one channel, the method comprising the steps of:producing, when fixed length cells designating said terminal as a destination of transmission are outputted from said exchange to said transmission line, a frame from the fixed length cells; translating the first logic channel information and the logic path information for the fixed length cells into the second logic channel information in the variable length frame; and providing said frame obtained in said producing step with the second logic information obtained in said translating step and inputting said frame with the second logic channel information in the variable length frame obtained in said translating step to said terminal.
 3. A variable length frame exchanging method by a fixed length cell handling exchange which handles fixed length cells each including a first logic channel information and a data section and to which a terminal adapted for a data communication using a variable length frame including a second logic channel information is connected by a transmission line having at least one channel, the method comprising the steps of:disassembling the variable length frame transmitted from said terminal into fixed length cells; converting the second logic channel information in the variable length frame into the first logic channel information for the fixed length cells; providing the first logic channel information obtained in said converting step for the fixed length cells obtained in said disassembling step and inputting the fixed length cells with the first logic channel information to said exchange; producing, when fixed length cells designating said terminal as a destination of transmission are outputted from said exchange to said transmission line, a frame from the fixed length cells; converting the first logic channel information for the fixed length cells into the second logic channel information in the variable length frame; and providing said frame obtained in said producing step and inputting said frame with the second logic channel information in the variable length frame obtained in said step of converting the first logic channel information, to said terminal.
 4. A variable length frame exchanging method by a fixed length cell handling exchange as claimed in claim 3, wherein the first logic channel information for the fixed length cells includes virtual path identifier information and virtual channel identifier information, and the second logic channel information includes a channel number or numbers of said transmission line which have been used to transmit the frame from said terminal and data link connection identifier information and wherein a first corresponding relationship between the virtual path identifier information and a channel number or numbers of said transmission line used between said terminal and said exchange and a second corresponding relationship between the virtual channel identifier information and a data link connection identifier to be provided to a frame are registered in advance, and wherein,when a frame is to be transmitted from said terminal to said exchange, a channel number or numbers of said transmission line which have been used to transmit the frame from said terminal of the second logic channel information are converted into virtual path identifier information of the first logic channel information in accordance with the first corresponding relationship and data link connection identifier information to be provided to the frame of the second logic channel information is converted into virtual channel identifier information of the first logic channel information in accordance with the second corresponding relationship, but when fixed length cells designating said terminal as a destination of transmission are outputted from said exchange to said subscriber line, virtual channel identifier information of the first logic channel information to be provided for the fixed length cells is converted into data link connection identifier information of the second logic channel information in accordance with the second corresponding relationship and virtual path identifier information of the first logic channel information to be provided for the fixed length cells is converted into a channel number or numbers of said transmission line which are available upon transmission of the frame to said terminal of the second logic channel information in accordance with the first corresponding relationship.
 5. A variable length frame exchanging interface apparatus which is interposed in a transmission line having at least one channel for interconnecting an exchange which handles fixed length cells each including a first logic channel information and a data section and a terminal adapted for a data communication using a variable length frame including a second logic channel information, and which performs conversion processing between the fixed length cells for said exchange and a variable length frame for said terminal, the apparatus comprising:frame production means for producing a frame based on data transmitted thereto from said terminal by a plurality of channels of said transmission line; wherein the first logic channel information includes virtual path identifier information and virtual channel identifier information and the second logic channel information includes a channel number or numbers of said transmission line which have been used to transmit the frame from said terminal and data link connection identifier information, first conversion means for converting a channel number or numbers of said transmission line which have been used to transmit the frame from said terminal of the second logic channel information in the variable length into virtual path identifier information of the first logic channel information for the fixed length cells; second conversion means for converting data link connection identifier information of the second logic channel information to be added to the frame into the virtual channel identifier information of the first logic channel information for the fixed length cells; and disassembling means for disassembling the frame into fixed length cells to which the virtual path identifier information obtained by conversion of said channel number or numbers into the virtual path identifier information in said first conversion means and the virtual channel identifier information obtained by conversion of said data link connection identifier information into the virtual channel identifier information in said second conversion means are added and sending out the fixed length cells with the added virtual path identifier information and the virtual channel identifier information to said exchange.
 6. A variable length frame exchanging interface apparatus as claimed in claim 5, wherein said first conversion means includes first storage means for storing in advance a first corresponding relationship between a channel number or numbers of said transmission line which are used between said terminal and said exchange and the virtual path identifier information, and said second conversion means includes second storage means for storing in advance a second corresponding relationship between a data link connection identifier to be added to the frame and the virtual channel identifier information.
 7. A variable length frame exchanging interface apparatus which is interposed in a transmission line having at least one channel for interconnecting an exchange which handles fixed length cells each including a first logic channel information and a data section and a terminal adapted for a data communication using a variable length frame including a second logic channel information, and which performs conversion processing between fixed length cells for said exchange and a variable length frame for said terminal, the apparatus comprising:frame assembling means for assembling a frame based on fixed length cells from said exchange designating said terminal as a destination of transmission; wherein the first logic channel information includes virtual path identifier information and virtual channel identifier information and the second logic channel information includes a channel number or numbers of said transmission line which have been used to transmit the frame from said terminal and data link connection identifier information, first conversion means for converting the virtual channel identifier information of the first logic channel information for the fixed length cells into the data link connection identifier information of the second logic channel information to be added to the frame; second conversion means for converting the virtual path identifier information of the first logic channel information for the fixed length cells into a channel number or numbers of said transmission line which are available upon transmission to said terminal of the second logic information; and frame disassembling means for disassembling and transmitting the frame, to which the data link connection identifier information obtained by conversion of said virtual channel identifier information into the data link connection identifier information in said first conversion means is added, by a channel or channels corresponding to the channel number or numbers of said transmission line obtained by conversion of said virtual path identifier information into the channel number or numbers in said second conversion means, to said terminal.
 8. A variable length frame exchanging interface apparatus as claimed in claim 7, wherein said second conversion means includes first storage means for storing in advance a first corresponding relationship between the virtual path identifier information and a channel number or numbers of said subscriber line which are used between said terminal and said exchange, and said first conversion means includes second storage means for storing in advance a second corresponding relationship between the virtual channel identifier information and a data link connection identifier to be added to a frame.
 9. A variable length frame exchanging interface apparatus which is interposed in a transmission line having at least one channel for interconnecting an exchange which handles fixed length cells each including a first logic channel information and a data section and a terminal adapted for a data communication using a variable length frame including a second logic channel information, and which performs conversion processing between fixed length cells for said exchange and a variable length frame for said terminal, the apparatus comprising:frame production means for producing a frame based on data transmitted thereto from said terminal by a plurality of channels of said transmission line; wherein the first logic channel information includes virtual path identifier information and virtual channel identifier information and the second logic channel information includes a channel number or numbers of said transmission line which have been used to transmit the frame from said terminal and data link connection identifier information, first conversion means for converting a channel number or numbers of said subscriber line which have been used to transmit the frame from said terminal of the second logic channel information into the virtual path identifier information of the first logic channel information for the fixed length cells; second conversion means for converting the data link connection identifier information of the second logic channel information to be added to the frame into the virtual channel identifier information of the first logic channel information for the fixed length cells; first frame disassembling means for disassembling the frame into fixed length cells to which the virtual path identifier information obtained by conversion of said channel number or numbers into the virtual path identifier information in said first conversion means and the virtual channel identifier information obtained by conversion of said data link connection identifier information into the virtual channel identifier information in said second conversion means are added and sending out the fixed length cells with the added virtual path identifier information and the virtual channel identifier information to said exchange; frame assembling means for assembling a frame based on the fixed length cells from said exchange designating said terminal as a destination of transmission; third conversion means for converting the virtual channel identifier information of the first logic channel information for the fixed length cells into the data link connection identifier information of the second logic channel information to be added to the frame; fourth conversion means for converting the virtual path identifier information of the first logic channel information for the fixed length cells into a channel number or numbers of said transmission line which are available upon transmission to said terminal of the second logic channel information; and second frame disassembling means for disassembling and transmitting the frame, to which the data link connection identifier information obtained by conversion of said virtual channel identifier information into the data link connection identifier information in said third conversion means is added, by a channel or channels corresponding to the channel number or numbers of said transmission line obtained by conversion of said virtual path identifier information into the channel number or numbers of said transmission line in said fourth conversion means, to said terminal.
 10. A variable length frame exchanging interface apparatus as claimed in claim 9, wherein said first conversion means and said fourth conversion means commonly include first storage means for storing in advance a first corresponding relationship between the virtual path identifier information and the channel number or numbers of said transmission line which are used between said terminal and said exchange; and said second conversion means and said third conversion means commonly include second storage means for storing in advance a second corresponding relationship between the virtual channel identifier information and the data link connection identifier information to be added to a frame.
 11. A call acceptance determination system for a fixed length cell handling exchange including one or more first terminals adapted for a data communication method using fixed length cells each including a first logic channel information and a data section and one or more second terminals adapted for a data communication using a variable length frame including a second logic channel information wherein said terminals are connected to said exchange by respective transmission lines, the system comprising:said exchange having a resource divided into a first terminal resource and a second terminal resource separate from each other; first terminal resource control means for controlling the first terminal resource and second terminal resource control means for controlling the second terminal resource; said first terminal resource control means including fixed length cell call acceptance determination means for determining whether or not a fixed length cell call from one of said first terminals should be accepted when the first terminal tries to use the first terminal resource; said second terminal resource control means including frame call acceptance determination means for determining whether or not a frame call from one of said second terminals should be accepted when the second terminal tries to use the second terminal resource.
 12. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 11, wherein said frame call acceptance determination means includes:virtual band calculation means for multiplying a use requested band requested to set from one of said second terminals by a predetermined multiplexing rate to calculate a use virtual band which is controlled by the network; subscriber line free band detection means for detecting a free band for said transmission lines for said second terminal; outgoing line free band detection means for detecting a free band for the outgoing lines for said second terminal; first comparison means for comparing the use requested band calculated by said virtual band calculation means and the free band detected by said subscriber line free band detection means with each other; second comparison means for comparing the use requested band calculated by said virtual band calculation means and the free band detected by said outgoing line free band detection means with each other; and call acceptance means for accepting a frame call from one of said second terminals when the comparison by said first comparison means proves that the use virtual band is smaller than the free band of said subscriber lines for said second terminals and the comparison by said second comparison means proves that the use virtual band is smaller than the free band for the outgoing lines for said second terminal.
 13. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 12, wherein a use requested band requested to set from one of said second terminals is added as band information to a frame call from the second terminal and is transmitted to said virtual band calculation means of said frame call acceptance determination means together with the frame call.
 14. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 11, wherein said frame call acceptance determination means includes:virtual band setting means for setting, when setting of a frame call is requested from one of said second terminals, a physical maximum speed of the second terminal as a use virtual band for the frame call; band assurance determination means for determining whether or not a band has been assured already for a same sending subscriber as the second terminal; free band detection means for detecting a free band for said lines for said second terminal: comparison means for comparing the use virtual band set by said virtual band setting means and the free band detected by said free band detection means with each other; and call acceptance means for accepting, when said band assurance determination means determines that a band has been assured already for the same sending subscriber as the second terminal, the frame call from the second terminal unconditionally and for assuring, when said band assurance determination means determines that no band has been assured as yet for the same sending subscriber as the second terminal and the comparison by said comparison means proves that the use virtual band is smaller than the free band for said lines for said second terminal, the use virtual band and accepting the frame call from the second terminal.
 15. A call acceptance determination system for a fixed length cell handling exchange accommodating one or more first terminals adapted for a data communication using fixed length cells each including a first logic channel information and a data section and one or more second terminals adapted for a data communication using a variable length frame including a second logic channel information wherein said terminals are connected to the exchange by respective transmission lines, the system comprising:first terminal subscriber resource control means for controlling a first terminal subscriber access resource for a case wherein a fixed length cell call from one of said first terminals is inputted to said exchange; second terminal subscriber resource control means for controlling a second terminal subscriber access resource for a case wherein a frame call from one of said second terminals is inputted to said exchange; and network resource control means for controlling a network common resource for a case wherein a fixed length cell call from one of said first terminals or a frame call from one of said second terminals is inputted to said exchange; said first terminal subscriber resource control means including fixed length cell call acceptance determination means for determining whether or not a fixed length cell call from one of said first terminals should be accepted when the first terminal tries to use the first terminal subscriber access resource; said second terminal resource control means including frame call acceptance determination means for determining whether or not a frame call from one of said second terminals should be accepted when the second terminal tries to use the second terminal subscriber access resource; said network resource control means including common resource call acceptance determination means for determining whether or not a fixed length cell call from one of said first terminals or a frame call from one of said second terminals should be accepted when the first terminal or the second terminal tries to use the network common resource.
 16. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 15, wherein said frame call acceptance determination means includes:virtual band calculation means for multiplying a use requested band requested to set from one of said second terminals by a predetermined multiplexing rate to calculate a use virtual band which is controlled by the network; incoming side subscriber line free band detection means for detecting a free band for the incoming side transmission lines for said second terminal; outgoing side subscriber line free band detection means for detecting a free band for the outgoing side transmission lines for said second terminal; first comparison means for comparing the use virtual band calculated by said virtual band calculation means and the free band detected by said incoming side subscriber line free band detection means with each other; second comparison means for comparing the use virtual band calculated by said virtual band calculation means and the free band detected by said outgoing side subscriber line free band detection means with each other; and call acceptance means for accepting a frame call from one of said second terminals when the comparison by said first comparison means proves that the use virtual band is smaller than the free band for said incoming side subscriber lines for said second terminal and the comparison by said second comparison means proves that the use virtual band is smaller than the free band for said outgoing side subscriber lines for said second terminal.
 17. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 16, wherein a use requested band requested to set from one of said second terminals is added as band information to a frame call from the second terminal and then transferred to said virtual band calculation means of said frame call acceptance determination means together with the frame call.
 18. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 15, wherein said common resource call acceptance determination means includes:virtual band calculation means for multiplying a use requested band requested to set from one of said first terminals or from one of said second terminals by a predetermined multiplexing rate to calculate a use virtual band which is controlled by the network; common resource free band detection means for detecting a free band on the network common resource of said exchange; comparison means for comparing the use virtual band calculated by said virtual band calculation means and the free band detected by said common resource free band detection means with each other; and call acceptance means for accepting a fixed length cell call from one of said first terminals or a frame call from one of said second terminals when the comparison by said comparison means proves that the use virtual band is smaller than the free band on the network common resource.
 19. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 16, wherein said common resource call acceptance determination means includes:virtual band calculation means for multiplying a use requested band requested to set from one of said first terminals or from one of said second terminals by a predetermined multiplexing rate to calculate a use virtual band which is controlled by the network; common resource free band detection means for detecting a free band on the network common resource of said exchange; comparison means for comparing the use virtual band calculated by said virtual band calculation means and the free band detected by said common resource free band detection means with each other; and call acceptance means for accepting a fixed length cell call from one of said first terminals or a frame call from one of said second terminals when the comparison by said comparison means proves that the use virtual band is smaller than the free band on the network common resource.
 20. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 17, wherein said common resource call acceptance determination means includes:virtual band calculation means for multiplying a use requested band requested to set from one of said first terminals or from one of said second terminals by a predetermined multiplexing rate to calculate a use virtual band which is controlled by the network; common resource free band detection means for detecting a free band on the network common resource of said exchange; comparison means for comparing the use virtual band calculated by said virtual band calculation means and the free band detected by said common resource free band detection means with each other; and call acceptance means for accepting a fixed length cell call from one of said first terminals or a frame call from one of said second terminals when the comparison by said comparison means proves that the use virtual band is smaller than the free band on the network common resource.
 21. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 18, wherein the predetermined multiplexing rate by which a use requested band is multiplied by said virtual band calculation means has two values set in advance including a first multiplexing rate for a use requested band requested to set from one of said first terminals and a second multiplexing rate for another use requested band requested to set from one of said second terminals.
 22. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 14, wherein the predetermined multiplexing rate by which a use requested band is multiplied by said virtual band calculation means has two values set in advance including a first multiplexing rate for a use requested band requested to set from one of said first terminals and a second multiplexing rate for another use requested band requested to set from one of said second terminals.
 23. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 20, wherein the predetermined multiplexing rate by which a use requested band is multiplied by said virtual band calculation means has two values set in advance including a first multiplexing rate for a use requested band requested to set from one of said first terminals and a second multiplexing rate for another use requested band requested to set from one of said second terminals.
 24. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 18, wherein a use requested band requested to set from one of said second terminals is added as band information to a frame call from the second terminal and then transferred to said virtual band calculation means of said common resource call acceptance determination means together with the frame call.
 25. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 19, wherein a use requested band requested to set from one of said second terminals is added as band information to a frame call from the second terminal and then transferred to said virtual band calculation means of said common resource call acceptance determination means together with the frame call.
 26. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 20, wherein a use requested band requested to set from one of said second terminals is added as band information to a frame call from the second terminal and then transferred to said virtual band calculation means of said common resource call acceptance determination means together with the frame call.
 27. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 21, wherein a use requested band requested to set from one of said second terminals is added as band information to a frame call from the second terminal and then transferred to said virtual band calculation means of said common resource call acceptance determination means together with the frame call.
 28. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 22, wherein a use requested band requested to set from one of said second terminals is added as band information to a frame call from the second terminal and then transferred to said virtual band calculation means of said common resource call acceptance determination means together with the frame call.
 29. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 23, wherein a use requested band requested to set from one of said second terminals is added as band information to a frame call from the second terminal and then transferred to said virtual band calculation means of said common resource call acceptance determination means together with the frame call.
 30. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 15, wherein said common resource call acceptance determination means includes:common resource fixed length cell call acceptance determination means for determining whether or not a fixed length cell call from one of said first terminals should be accepted when the first terminal tries to use the network common resource; and common resource frame call acceptance determination means for determining whether or not a frame call from one of said second terminals should be accepted when the second terminal tries to use the network common resource.
 31. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 30, wherein said common resource frame call acceptance determination means includes:virtual band setting means for setting, when setting of a frame call is requested from one of said second terminals, a physical maximum speed of the second terminal as a use virtual band for the frame call; band assurance determination means for determining whether or not a band has been assured already for a same sending subscriber as the second terminal on the network common resource; common resource free band detection means for detecting a free band on the network common resource of said exchange; comparison means for comparing the use virtual band set by said virtual band setting means and the free band detected by said common resource free band detection means with each other; and call acceptance means for accepting, when said band assurance determination means determines that a band has been assured already for the same sending subscriber as the second terminal, the frame call from the second terminal unconditionally and for assuring, when said band assurance determination means determines that no band has been assured as yet for the same sending subscriber as the second terminal and the comparison by said comparison means proves that the use virtual band is smaller than the free band on the network common resource, the use virtual band and accepting the frame call from the second terminal.
 32. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 30, wherein said common resource frame call acceptance determination means includes:virtual band setting means for setting a use requested band requested to set for a frame call from one of said second terminals as a use virtual band for the frame call; band assurance determination means for determining whether or not a band has been assured already for a same sending subscriber as the second terminal on the network common resource; common resource free band detection means for detecting a free band on the network common resource of said exchange; first comparison means for comparing, when said band assurance determination means determines that no band has been assured as yet for the same sending subscriber as the second terminal, the use virtual band set by said virtual band setting means and the free band detected by said common resource free band detection means with each other; assured band extraction means for extracting, when said band assurance determination means determines that a band has been assured for the same sending subscriber as the second terminal, the band assured already for the second terminal; second comparison means for comparing the band extracted by said assured band extraction means and a physical maximum speed of the second terminal with each other; third comparison means for comparing, when the comparison by said second comparison means proves that the band extracted by said assured band extraction means is equal to or lower than the physical maximum speed of the second terminal, a sum of the band extracted by said assured band extraction means and the use virtual band set by said virtual band setting means and the physical maximum speed of the second terminal with each other; remaining available band calculation means for subtracting, when the comparison by said third comparison means proves that the sum is higher than the physical maximum speed of the second terminal, the band extracted by said assured band extraction means from the physical maximum speed of the second terminal to calculate a remaining available band; fourth comparison means for comparing the remaining available band calculated by said remaining available band calculation means and the free band detected by said common resource free band detection means with each other; fifth comparison means for comparing, when the comparison by said third comparison means proves that the sum is equal to or lower than the physical maximum speed of the second terminal, the use virtual band set by said virtual band setting means and the free band detected by said common resource free band detection means with each other; and call acceptance means for assuring, when the comparison by said first comparison means or said fifth comparison means proves that the use virtual band is smaller than the free band on the common resource, the use virtual band and accepting the frame call from the second terminal, for assuring, when the comparison by said fourth comparison means proves that the remaining available band is smaller than the free band on the common resource, the remaining available band and accepting the frame call from the second terminal, and for accepting, when the comparison by said second comparison means proves that the band extracted by said assured band extraction means is higher than the physical maximum speed of the second terminal, the frame call from the second terminal unconditionally.
 33. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 32, wherein, for each of said second terminals connected to said exchange by way of said respective subscriber lines, a use band table is provided for controlling and storing a physical maximum speed of the second terminal and a sum total of use requested bands which have been requested to set before the present point of time by the second terminal, and said assured band extraction means extracts the sum total of the use requested bands of the use band table as a band assured already for the second terminal whereas the physical maximum speed of the second terminal which is to be used by said second comparison means, said third comparison means and said remaining available band calculation means is read out from the use band table.
 34. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 32, wherein a use requested band requested to set from one of said second terminals is added as band information to a frame call from the second terminal and then transferred to said virtual band setting means of said common resource frame call acceptance determination means together with the frame call.
 35. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 33, wherein a use requested band requested to set from one of said second terminals is added as band information to a frame call from the second terminal and then transferred to said virtual band setting means of said common resource frame call acceptance determination means together with the frame call.
 36. A variable length frame exchanging interface apparatus which is interposed in a transmission line having at least one channel for interconnecting an exchange which handles fixed length cells each including a first logic channel information, a logic path information and a data section and a terminal adapted for a data communication using a variable length frame including a second logic channel information and which performs conversion processing between the fixed length cells for said exchange and a variable length frame for said terminal, the apparatus comprising:frame disassembling means for disassembling the variable length frame transmitted from said terminal into fixed length cells; translation means for translating the second logic channel information in the variable length frame into the first logic channel information and the logic path information for the fixed length cells; and means for providing the first logic channel information, and the logic path information obtained in said translation means for the fixed length cells obtained in said frame disassembling means and inputting the fixed length cells with the first logic channel information and the logic path information to said exchange.
 37. A variable length frame exchanging interface apparatus which is interposed in a transmission line having at least one channel for interconnecting an exchange which handles fixed length cells each including a first logic channel information, a logic path information and a data section and a terminal adapted for a data communication using a variable length frame including a second logic channel information and which performs conversion processing between the fixed length cells for said exchange and a variable length frame for said terminal, the apparatus comprising:means for producing, when fixed length cells designating said terminal as a destination of transmission are outputted from said exchange to said transmission line, a frame from the fixed length cells; translation means for translating the first logic channel information and the logic path information for the fixed length cells into the second logic channel information in the variable length frame; and means for providing said frame obtained in said producing means with the second logic information obtained in said conversion means and inputting said frame with the second logic channel information in the variable length frame obtained in said translation means to said terminal.
 38. A variable length frame exchanging interface apparatus which is interposed in a transmission line having at least one channel for interconnecting an exchange which handles fixed length cells each including a first logic channel information and a data section and a terminal adapted for a data communication using a variable length frame including a second logic channel information and which performs conversion processing between the fixed length cells for said exchange and a variable length frame for said terminal, the apparatus comprising:frame disassembling means for disassembling the variable length frame transmitted from said terminal into fixed length cells; first conversion means for converting the second logic channel information in the variable length frame into the first logic channel information for the fixed length cells; first means for providing the first logic channel information obtained in said first conversion means for the fixed length cells obtained in said frame disassembling means and inputting the fixed length cells with the first logic channel information to said exchange; means for producing, when fixed length cells designating said terminal as a destination of transmission are outputted from said exchange to said transmission line a frame from the fixed length cells; second conversion means for converting the first logic channel information for the fixed length cells into the second logic channel information in the variable length frame; and second means for providing said frame obtained in said producing means with the second logic channel information obtained in said second conversion means and inputting said frame with the second logic channel information in the variable length frame obtained in said second conversion means to said terminal. 